Transferrin saturation (% saturation transferrin or TSAT) is the percent of the iron-binding protein transferrin that is occupied by iron. The test measures serum iron relative to the total iron-binding capacity (TIBC) and indicates how much circulating iron is available for tissues and red blood cell production.

Alkaline phosphatase (ALP) is an enzyme present in liver, bone, placenta, intestine and kidney; the serum ALP test measures ALP activity in blood. It is used to detect and monitor conditions that increase bone turnover (Paget’s disease, bone healing, metastases) or cause cholestasis/hepatobiliary disease (bile duct obstruction, primary biliary cholangitis).

Anti-Müllerian hormone (AMH) is a glycoprotein produced by granulosa cells of small growing ovarian follicles and is a marker of the remaining egg (ovarian) reserve. The blood test measures circulating AMH concentration to estimate quantity (not quality) of a woman’s follicle pool.

Antinuclear antibody (ANA) titer measures the presence and concentration of autoantibodies that bind components of the cell nucleus. It is a screening test for systemic autoimmune diseases such as systemic lupus erythematosus (SLE), Sjögren’s syndrome, systemic sclerosis, mixed connective tissue disease and some autoimmune liver disorders.

The APO B : APO A (ApoB/ApoA1) ratio is the proportion of apolipoprotein B (the main protein on atherogenic particles such as LDL and VLDL) to apolipoprotein A‑I (the principal protein of protective HDL particles). The test measures circulating ApoB and ApoA1 concentrations and calculates their ratio to estimate the balance between atherogenic and anti‑atherogenic lipoproteins.

Antistreptolysin O (ASO) quantitative measures antibodies directed against streptolysin O, a toxin produced by Group A Streptococcus (GAS). The test estimates whether a recent streptococcal infection has occurred—useful when considering complications such as acute rheumatic fever, post‑streptococcal reactive arthritis, or post‑streptococcal glomerulonephritis.

Absolute basophil count measures the number of basophils — a rare type of white blood cell — in a given volume of blood. Basophils play roles in allergic and inflammatory responses by releasing histamine, heparin and other mediators, and participate in immune surveillance.

Absolute eosinophil count measures the number of eosinophils — a type of white blood cell involved in immune responses to parasites, allergic reactions and certain inflammatory processes — per unit of blood. It is calculated from the complete blood count (CBC) with differential and reflects the true eosinophil burden rather than a percentage.

Absolute immature granulocytes (IG#) measures the number of early neutrophil-lineage cells (promyelocytes, myelocytes, metamyelocytes) circulating in peripheral blood. It is reported as an absolute count and reflects bone marrow release of immature granulocytes during increased demand or disrupted maturation.

The Absolute Lymphocyte Count (ALC) is a CBC parameter that measures the total number of lymphocytes (T cells, B cells, and NK cells) in a given volume of blood. Lymphocytes are white blood cells central to adaptive and innate immune responses.

The absolute monocyte count (AMC) measures the number of monocytes — a type of white blood cell — in a given volume of blood. Monocytes are part of the innate immune system and mature into macrophages and dendritic cells that clear pathogens and debris and help regulate inflammation.

Absolute neutrophil count (ANC) measures the number of neutrophils — a type of white blood cell that is a first-line defender against bacteria and fungi — in a microliter or litre of blood. It is calculated from the white blood cell count and the percentage of neutrophils (including bands) on the differential.

Large Unstained Cells (absolute count) (often abbreviated LUC# or ALUC) are a component reported by modern automated complete blood count (CBC) analyzers. The instrument flags and counts cells that are larger than typical lymphocytes and that do not take up the usual staining pattern used by the analyzer — a heterogeneous group that can include atypical/reactive lymphocytes, blasts (immature white cells), immature granulocytes, large granular lymphocytes, plasma cells or monocytes.

Absolute nucleated red blood cells (NRBCs) are immature erythroid precursors that still contain a nucleus. The test measures the absolute number of NRBCs in peripheral blood (usually reported as cells/µL or cells per 100 white blood cells).

Ascorbic acid (vitamin C) in urine measures how much vitamin C is being excreted by the kidneys and reflects recent dietary intake, supplementation and renal handling. The test helps assess vitamin C status (possible deficiency or excess), monitors high-dose supplementation or intravenous therapy, and can explain unexpected urine dipstick results because ascorbic acid can interfere with some chemical tests.

Acetone is one of the three ketone bodies produced during fatty acid breakdown (along with acetoacetate and beta‑hydroxybutyrate). A urine acetone (ketone) test detects ketone bodies that spill into the urine when carbohydrate availability is low or fat metabolism is increased.

Activated Partial Thromboplastin Time (aPTT) is a blood test that measures how long it takes blood to clot via the intrinsic and common coagulation pathways. It evaluates the function of clotting factors VIII, IX, XI, XII and the common pathway factors (II, V, X and fibrinogen) and detects inhibitors to these factors.

Albumin is the most abundant protein in blood plasma, produced by the liver. It helps maintain oncotic (colloid osmotic) pressure, transports hormones, fatty acids, bilirubin and many drugs, and serves as a reservoir of amino acids.

The albumin:globulin (A/G) ratio compares the blood concentration of albumin (the main plasma protein made by the liver) to total globulins (a group of proteins including antibodies). The test measures the relative amounts of these protein groups and is calculated from measured serum albumin and total protein.

Albuminuria is the abnormal presence of the blood protein albumin in urine, reflecting increased permeability of the glomerular filtration barrier or impaired tubular reabsorption. The test measures urinary albumin excretion—commonly reported as a spot urine albumin-to-creatinine ratio (ACR) or as albumin excreted per day—to detect early kidney damage.

Alpha-fetoprotein (AFP) is a fetal glycoprotein produced mainly by the fetal liver and yolk sac. The AFP blood test measures the concentration of this protein in serum.

Amorphous deposits on urine microscopy are non‑crystalline granular precipitates composed primarily of amorphous urates (in acidic urine) or amorphous phosphates (in alkaline urine). The urine sediment exam identifies their presence and general amount (absent, few, moderate, many).

Amylase is an enzyme produced mainly by the pancreas and the salivary glands that helps digest carbohydrates by breaking starch into simpler sugars. The serum amylase test measures the amount of amylase circulating in the blood and is used primarily to evaluate suspected pancreatic injury or inflammation (for example, acute or chronic pancreatitis).

Androstenedione is an androgenic steroid produced mainly by the adrenal glands and the gonads (ovaries in females, testes in males). It is a biochemical precursor to testosterone and estrone (an estrogen).

Anti‑CCP (anti‑cyclic citrullinated peptide) antibodies are autoantibodies directed against citrullinated proteins produced when arginine residues are post‑translationally modified. The anti‑CCP blood test measures the presence and titer of these antibodies, most often IgG, and is used primarily to detect and help predict rheumatoid arthritis (RA).

Anti‑cardiolipin IgA (aCL IgA) is an autoantibody directed against cardiolipin, a phospholipid present on cell membranes and platelets. The test measures IgA-class anticardiolipin antibodies, usually by ELISA, as part of antiphospholipid antibody evaluation.

Anti‑cardiolipin IgG is an autoantibody directed against cardiolipin, a phospholipid found on cell membranes. The laboratory test measures the concentration of IgG-class anticardiolipin antibodies, reported in GPL (IgG phospholipid) units, and is used to detect antiphospholipid antibodies that promote abnormal blood clotting.

Anti‑cardiolipin IgM are autoantibodies directed against cardiolipin, a phospholipid found on cell membranes. The test measures the IgM isotype of anticardiolipin antibodies in the blood.

Anti-DNA antibodies are autoantibodies directed primarily against double‑stranded DNA (anti-dsDNA) produced when the immune system targets the body’s own genetic material. The test measures the presence and amount (titer) of these antibodies in blood, helping to detect and monitor systemic lupus erythematosus (SLE) and to assess disease activity—especially lupus nephritis.

Anti‑HCV (antibodies to hepatitis C virus) is an immunologic test that detects antibodies produced in response to HCV infection. The assay measures whether the immune system has seen HCV proteins, indicating past or current exposure; it does not directly measure virus (HCV RNA).

Anti‑nuclear antibodies (ANA) are autoantibodies that target components of the cell nucleus. The ANA test detects these antibodies using indirect immunofluorescence (titer and pattern) or immunoassays (units).

Anti-thyroglobulin antibodies (Anti‑Tg Abs) are autoantibodies directed against thyroglobulin, a protein made by thyroid follicular cells that is essential for thyroid hormone synthesis. The laboratory test measures the concentration of these antibodies in blood to detect autoimmune activity against the thyroid.

Anti-phospholipid (IgG) refers to IgG-class antibodies that bind phospholipids or phospholipid‑binding proteins (most commonly cardiolipin or β2‑glycoprotein I). The test measures the concentration of these IgG antibodies in blood to detect immune activity that promotes blood clotting.

Anti‑TPO (anti–thyroid peroxidase) antibodies are immune proteins directed against thyroid peroxidase, an enzyme required for thyroid hormone synthesis. The serum anti‑TPO test measures the presence and titre of these antibodies to detect autoimmune attack on the thyroid.

Anti–tissue transglutaminase IgA (tTG‑IgA) is an autoantibody directed against the enzyme tissue transglutaminase in the intestinal mucosa. The blood test measures IgA class antibodies to tTG and is used primarily to screen for and support diagnosis of celiac disease (immune‑mediated enteropathy triggered by gluten).

Apo A (usually measured as apolipoprotein A‑I or Apo A1) is the main protein component of high‑density lipoprotein (HDL). The test measures the blood concentration of Apo A1, reflecting HDL particle number and reverse cholesterol transport capacity.

Apolipoprotein B (Apo B) is the main structural protein of atherogenic lipoprotein particles — primarily VLDL, IDL, LDL and Lp(a). The Apo B test measures the circulating concentration of this protein and therefore serves as a surrogate for the number of atherogenic lipoprotein particles that can deposit cholesterol in arterial walls.

Appearance in a urine analysis refers to the visual characteristics of a urine specimen — primarily its color and clarity (clarity ranges from clear to turbid). The test is a rapid, first-line assessment that reflects hydration status and the presence of cells, bacteria, crystals, lipids, blood, or pigment.

Atypical lymphocytes (often reported as LUC — large unstained cells or “reactive” lymphocytes) are white blood cells with an activated or abnormal appearance on a peripheral blood film. The test measures the proportion or absolute number of these cells as part of a complete blood count (CBC) with differential.

The BUN : Creatinine ratio compares blood urea nitrogen (BUN) to serum creatinine to help identify the likely cause of kidney-related abnormalities. BUN is produced from protein metabolism and cleared by the kidneys; creatinine comes from muscle breakdown and is also renally cleared.

Bacteria on urine analysis refers to the detection of microorganisms in a urine specimen, either by microscopic examination or by quantitative urine culture. The test measures presence and (with culture) the number of colony-forming units per milliliter (CFU/mL), which helps distinguish contamination from true urinary tract infection (UTI).

Basophils are a type of white blood cell (granulocyte) produced in the bone marrow that normally make up a very small fraction of circulating leukocytes. They contain histamine, heparin and other mediators and participate in allergic responses, inflammation, and immune regulation.

Bile pigment in a urine test refers primarily to bilirubin (the water‑soluble, conjugated form) and related biliary pigments that may appear in urine when the liver’s ability to excrete bilirubin into bile is impaired or bile flow is obstructed. The urine test detects bilirubin (and, separately, urobilinogen patterns) as a sign of hepatobiliary disease.

Bile salts (conjugated bile acids) are detergents made by the liver from cholesterol and secreted into bile to help digest and absorb dietary fats. A urine bile salts test detects whether these compounds are present in urine — normally they are absent because bile salts are excreted into the intestine and largely reabsorbed by the gut.

Bilirubin in a urine analysis detects conjugated (direct) bilirubin that has been processed by the liver and is water-soluble. Bilirubin itself is produced by breakdown of heme from red blood cells; unconjugated bilirubin is lipid-soluble and not normally excreted in urine.

Blast cells are immature precursor white blood cells normally confined to the bone marrow; they include myeloblasts and lymphoblasts that mature into functional granulocytes or lymphocytes. A CBC with peripheral blood differential or a blood smear looks for blasts circulating in blood; their presence suggests bone marrow disruption.

The "Blood" parameter in a urine analysis detects red blood cells (RBCs), free hemoglobin, or myoglobin in the urine. The test measures either a reagent-strip (dipstick) reaction for peroxidase activity (detecting hemoglobin/myoglobin) and/or microscopic RBC count on spun urine.

Blood group testing determines a person’s ABO type (A, B, AB or O) and RhD status (Positive or Negative). The test identifies antigens on red blood cell surfaces and corresponding antibodies in plasma.

Fasting blood sugar (fasting plasma glucose) measures the concentration of glucose in the blood after an overnight (usually 8–12 hour) fast. It reflects how well the body maintains baseline blood glucose through insulin secretion and glucose uptake by tissues.

Postprandial blood sugar (PPBS) measures the concentration of glucose in the blood after eating, typically measured two hours after a meal. It evaluates how effectively the body produces and uses insulin to clear glucose from the circulation.

Random blood sugar (also called casual plasma glucose) measures the glucose concentration in blood at any time of day, regardless of last meal. It reflects how well the body manages blood glucose between meals and during everyday activities.

Blood urea (often reported as BUN — blood urea nitrogen — or as serum urea) is a waste product formed in the liver from breakdown of proteins and amino acids; it carries excess nitrogen to the urine. The blood urea test measures how much urea is circulating and is used to assess kidney excretory function and protein metabolic state.

Blood Urea Nitrogen (BUN) measures the amount of nitrogen in the blood that comes from urea, a waste product formed in the liver when the body breaks down protein. The BUN test evaluates how well the kidneys are filtering and excreting urea and can indicate kidney function, hydration status, and protein metabolism.

CA 125 (cancer antigen 125) is a glycoprotein produced by cells derived from coelomic and Müllerian epithelium; the blood test measures the concentration of this antigen (reported in U/mL). It is most widely used as a tumor marker for ovarian cancer—both for monitoring treatment response and detecting recurrence—but can be raised in other malignancies (endometrial, peritoneal, pancreatic, breast, lung) and many benign conditions.

CA 15-3 (Cancer Antigen 15-3) is a circulating fragment of the MUC1 glycoprotein found on epithelial cells. The blood test measures the level of this tumor-associated antigen.

CA 19-9 (carbohydrate antigen 19-9, sialyl‑Lewis A) is a tumor‑associated glycoprotein shed into the blood by epithelial cells of the pancreas, bile ducts and gastrointestinal tract. The blood test measures serum CA 19-9 concentration and is used primarily as an adjunct marker for pancreatic cancer—also elevated in cholangiocarcinoma, gastric and colorectal cancers—and to monitor treatment response or recurrence.

Carcinoembryonic antigen (CEA) is a glycoprotein normally produced during fetal development and present at very low levels in healthy adults. The blood test measures circulating CEA concentration and is used primarily as a tumor marker—most commonly in colorectal cancer—though levels can be raised in other malignancies (pancreas, stomach, breast, lung) and in several benign conditions.

CK‑MB is the creatine kinase isoenzyme that is relatively specific to heart muscle (myocardium). The CK‑MB test measures the concentration or activity of this isoenzyme in blood and is used to detect myocardial cell injury or necrosis that releases intracellular enzymes into the circulation.

Cytomegalovirus (CMV) IgG is an antibody produced by the immune system after exposure to CMV, a common herpesvirus. The CMV IgG test measures the presence and amount of these long-lived antibodies to determine past infection or immune status.

COVID-19 IgM is an immunoglobulin M antibody test that detects early humoral immune response to SARS-CoV-2 infection. The assay measures IgM class antibodies directed against viral proteins; IgM typically appears within about 5–10 days after infection onset, peaks in the second to third week, and then declines.

The COVID Antibody test measures antibodies produced by the immune system against SARS-CoV-2 (the virus that causes COVID-19). Tests commonly detect IgG, IgM, or total antibodies directed to viral proteins (spike or nucleocapsid), indicating prior infection or response to vaccination.

COVID RT‑PCR (reverse transcription polymerase chain reaction) is a molecular test that detects SARS‑CoV‑2 viral RNA in respiratory specimens (commonly nasopharyngeal/oropharyngeal swabs, nasal swabs, or saliva). The test measures presence — not live virus — and is used to diagnose current (acute) COVID‑19 infection.

C‑reactive protein (CRP) is an acute‑phase protein produced by the liver in response to inflammation (mainly driven by IL‑6). The blood test measures circulating CRP concentration as a nonspecific marker of inflammation or tissue injury.

Candida in urine (candiduria) refers to the presence of Candida species (yeasts) detected by urine microscopy, dipstick, or culture. The test measures whether yeast cells or colony-forming units (CFU) are present in a urine specimen and, if cultured, may identify the species.

Casts are microscopic, tube-shaped particles formed in the renal tubules and collecting ducts from precipitation of Tamm-Horsfall protein mixed with cellular elements. Urine microscopy for casts evaluates number and type (hyaline, RBC, WBC, granular, waxy, fatty, epithelial) to help localize kidney disease.

Chlamydia IgM is a blood test that detects IgM-class antibodies directed against Chlamydia trachomatis. IgM antibodies typically arise early after exposure and so their presence suggests recent or acute infection rather than remote or past exposure (which is better indicated by IgG).

The Indirect Coombs test (indirect antiglobulin test, IAT) detects antibodies directed against red blood cell (RBC) surface antigens that are present in a patient’s serum but not bound to cells. It measures whether circulating alloantibodies or autoantibodies exist that could react with donor blood or fetal RBCs.

Cortisol (serum, p.m.) measures the blood level of cortisol in the evening, when healthy people normally have low concentrations because cortisol follows a strong diurnal (day–night) rhythm driven by ACTH from the pituitary. The evening (late‑day/bedtime) value is used to detect loss of normal nightly suppression — a hallmark of Cushing’s syndrome — and to help evaluate adrenal insufficiency.

COVID-19 IgG is an antibody test that detects immunoglobulin G directed against SARS-CoV-2 (the virus that causes COVID-19). It measures whether a person has developed a longer‑term adaptive immune response from prior infection or vaccination (usually appearing 1–3 weeks after exposure).

Creatine kinase (CK) is an enzyme mainly found in heart, skeletal muscle and brain that helps regenerate cellular energy by converting creatine and ATP. The CK test measures total CK activity in blood; higher levels indicate damage to muscle cells releasing CK into circulation.

Urine "crystals" are microscopic solid formations of dissolved minerals and organic compounds that precipitate in the urinary tract when urine becomes supersaturated, concentrated, or has an abnormal pH. A urine microscopy test looks for presence, quantity (rare/few/moderate/many), and crystal type (e.g., calcium oxalate, uric acid, struvite, cystine, bilirubin, tyrosine).

The Cycle Threshold (Ct) for the E-gene is a value produced by real-time RT‑PCR assays that detect SARS‑CoV‑2 RNA. It represents the number of amplification cycles required for fluorescent signal from the E (envelope) gene target to cross a predefined threshold; lower Ct = more viral RNA in the sample (higher viral load).

The Cycle Threshold (Ct) for the N-gene is the number of PCR amplification cycles required to detect SARS-CoV-2 RNA targeting the viral nucleocapsid (N) gene. It is reported by real-time RT‑PCR tests used to diagnose COVID-19.

The Cycle Threshold (Ct) for the ORF1a gene is the number of PCR amplification cycles required to detect SARS‑CoV‑2 RNA targeting the ORF1a region. It does not measure virus infectivity directly but is inversely related to viral RNA quantity: lower Ct = higher viral RNA load.

The Cycle Threshold (Ct) for the RdRp (RNA-dependent RNA polymerase) target is a numeric result from a SARS‑CoV‑2 RT‑PCR test that indicates how many amplification cycles were required to detect viral RNA specific to the RdRp gene. Lower Ct values mean more viral RNA in the specimen (higher viral load); higher Ct values mean less RNA.

D‑dimer is a small protein fragment produced when a blood clot is broken down by the body’s fibrinolytic system. The D‑dimer test measures the amount of this fragment in blood and indicates recent or ongoing clot formation and degradation.

"Deposits" in a urine analysis refers to the cellular and particulate material found in the urine sediment after centrifugation (cells, casts, crystals, bacteria, mucus and epithelial fragments). The test evaluates type and quantity of these deposits to detect kidney or urinary tract pathology.

DHEA‑sulphate (DHEA‑S) is a sulphated adrenal androgen produced mainly by the adrenal cortex; it is a stable circulating form of dehydroepiandrosterone and serves as a marker of adrenal androgen production. The DHEA‑S test measures serum DHEA‑S concentration to evaluate causes of excess or deficient androgen activity.

The Dengue NS1 test detects the nonstructural protein 1 (NS1) antigen of dengue virus in blood; NS1 is produced and secreted by infected cells during active viral replication. The assay is used to identify acute dengue infection, especially in the early febrile phase (typically days 0–9 after symptom onset, most sensitive days 0–5).

Direct bilirubin (conjugated bilirubin) is the water‑soluble form of bilirubin produced when the liver adds glucuronic acid to unconjugated bilirubin so it can be excreted in bile. The direct bilirubin test measures the conjugated fraction in blood and helps distinguish liver excretory problems from increased bilirubin production.

The erythrocyte sedimentation rate (ESR) measures how quickly red blood cells settle in a vertical tube over one hour. It is a nonspecific marker of inflammation: elevated acute‑phase proteins (fibrinogen, immunoglobulins) promote red cell stacking (rouleaux) and faster settling.

Eosinophils are a type of white blood cell (granulocyte) involved in immune responses against parasites and in allergic inflammation. A CBC with differential measures their absolute number and percentage of total white cells.

Epithelial cells in a urine test are cells that line the urinary tract (squamous cells from the distal urethra/vagina, transitional cells from the bladder/ureters/renal pelvis, and renal tubular epithelial cells from the kidney tubules). The urine sediment examination measures the number and type of these cells to help distinguish contamination from true urinary tract pathology.

Estradiol (E2) is the primary biologically active estrogen produced mainly by the ovaries in females and in smaller amounts by the testes and peripheral tissues in males. The blood test measures circulating estradiol concentration to assess ovarian function, menstrual cycle status and estrogen exposure.

Estrogen refers mainly to the group of female sex hormones (estradiol is the principal form measured for fertility). The test quantifies circulating estradiol to assess ovarian function, timing of ovulation, and response to fertility treatments.

Follicle-stimulating hormone (FSH) is a pituitary gonadotropin that regulates ovarian follicle growth and estrogen production in women and stimulates spermatogenesis in men. The blood test measures circulating FSH to assess pituitary–gonadal axis function.

Ferritin is an intracellular protein that stores iron and releases it in a controlled fashion; serum ferritin concentration reflects the body’s iron stores and is the most useful single test to assess iron status. The ferritin test measures circulating ferritin in blood to help detect iron deficiency, iron overload (hemochromatosis), and assess inflammation or chronic disease.

Free T3 (triiodothyronine, FT3) is the unbound, biologically active form of the thyroid hormone T3 circulating in blood. The FT3 test measures the free T3 available to tissues (not the protein-bound fraction) and helps assess thyroid function and metabolic state.

Free T4 (free thyroxine) is the unbound fraction of the thyroid hormone thyroxine circulating in blood; it is the biologically active form available to tissues. The Free T4 test measures the concentration of this unbound hormone to assess thyroid gland function and help diagnose hyperthyroidism or hypothyroidism, thyroiditis, and to monitor replacement or antithyroid therapy.

Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme in red blood cells that helps protect them from oxidative damage by maintaining reduced glutathione. The quantitative G6PD assay measures enzyme activity (usually reported as U/g hemoglobin) to detect deficiency.

Gamma‑glutamyl transferase (GGT) is an enzyme found mainly in liver cells and biliary epithelium; the blood test measures circulating GGT activity. It is a sensitive marker of hepatobiliary injury and enzyme induction rather than a specific disease test.

Globulin refers to a group of serum proteins (alpha, beta and gamma globulins) that include transport proteins, acute‑phase reactants and immunoglobulins (antibodies). The laboratory "globulin" value is usually calculated as total serum protein minus albumin and reflects the combined non‑albumin proteins in blood.

Glomerular Filtration Rate (GFR) measures how much blood the kidneys filter each minute, normalized to body surface area (mL/min/1.73 m²). It is estimated (eGFR) from blood creatinine (and sometimes cystatin C), age, sex and body size to assess kidney function.

Glomerular Filtration Rate (reported as eGFR) estimates how much blood the kidneys filter each minute, normalized to body surface area (mL/min/1.73 m²). It is calculated from serum creatinine plus age, sex and sometimes race, and is the key measure used to detect and stage chronic kidney disease (CKD).

Glucose in urine (urinary glucose, glycosuria) measures whether sugar (glucose) is being excreted by the kidneys. Normally the kidney reabsorbs all filtered glucose so urine contains no detectable glucose.

The Gram stain is a rapid, microscopic staining technique that classifies bacteria as Gram-positive (purple) or Gram-negative (pink) and shows basic bacterial shape (cocci, bacilli) and arrangement. It is applied to clinical specimens (sputum, urine, CSF, wound swabs, synovial fluid, blood culture smears) to detect and give early clues about bacterial infection and guide empiric therapy.

Growth hormone (GH, somatotropin) is a peptide hormone secreted by the anterior pituitary that stimulates linear growth, protein synthesis, and influences carbohydrate and fat metabolism through direct action and by increasing IGF‑1 production in the liver. A serum GH test measures circulating GH but because GH is secreted in short pulses (highest at night and during sleep/exercise), single random values are hard to interpret.

HAV Ab (Hepatitis A virus antibody) testing detects antibodies produced in response to HAV infection or vaccination. Tests commonly measure anti-HAV IgM (marker of recent/acute infection) and anti-HAV IgG/total anti-HAV (marker of past infection or immunity).

HAV Ab IgM is an immunoglobulin M antibody produced by the immune system in response to infection with hepatitis A virus (HAV). The test detects recent or acute HAV infection by measuring IgM-class antibodies directed against HAV.

HAV AB Total (total antibody to hepatitis A virus) measures the combined presence of IgM and IgG antibodies against hepatitis A virus (HAV) in blood. The test detects recent or past HAV exposure or vaccine-induced immunity: IgM indicates recent/acute infection, while IgG indicates prior infection or successful vaccination and usually long-term immunity.

HBcAb Total (total antibody to hepatitis B core antigen, anti-HBc Total) is a serologic marker that detects both IgM and IgG antibodies directed against the core protein of hepatitis B virus (HBV). The test does not distinguish between recent and past infection by itself (IgM vs IgG), but a positive result shows prior exposure to HBV—either acute, resolving, or remote/chronic infection.

HBsAb (Hepatitis B surface antibody, also called anti-HBs) is an antibody produced by the immune system against the hepatitis B virus surface antigen (HBsAg). The test measures the presence and quantity of these antibodies in blood to determine whether a person is immune to hepatitis B because of past infection or vaccination.

Hepatitis B surface antigen (HBsAg) is a protein on the outer shell of the hepatitis B virus (HBV). The HBsAg blood test detects this antigen and therefore indicates active HBV infection (either acute or chronic).

The HCV Ab (Hepatitis C antibody) test detects antibodies produced by the immune system in response to infection with hepatitis C virus (HCV). It does not directly detect the virus but indicates whether a person has been exposed to HCV in the past or currently.

HDL cholesterol (high-density lipoprotein cholesterol) is the fraction of blood cholesterol carried in HDL particles that participate in reverse cholesterol transport — moving cholesterol from tissues and artery walls back to the liver for excretion. The HDL test measures the concentration of cholesterol in HDL particles and is reported as part of a lipid profile to assess cardiovascular risk.

Haemoglobin Distribution Width (HDW) is a red‑cell index that quantifies the variation in haemoglobin concentration among individual erythrocytes. It is derived from the haemoglobin concentration histogram produced by automated haematology analysers and reflects how uniformly haemoglobin is distributed across the red cell population.

HIV AB refers to testing for antibodies produced by the immune system in response to infection with human immunodeficiency virus (HIV) — commonly HIV‑1 and HIV‑2. Modern immunoassays often combine antibody detection with p24 antigen detection (4th‑generation tests) but the “HIV AB” result specifically denotes antibody reactivity.

The HIV Combo (Ag+Ab) test is a fourth‑generation screening assay that detects both HIV p24 antigen (an early viral protein) and antibodies to HIV‑1 and HIV‑2. By measuring antigen and antibody it shortens the diagnostic window and can identify acute (very recent) and established infections.

Haematocrit (Hct) is the proportion of blood volume made up by red blood cells, reported as a percentage. The test measures the packed cell volume after centrifugation and helps assess oxygen-carrying capacity.

Haemoglobin is the oxygen-carrying protein inside red blood cells that binds oxygen in the lungs and delivers it to tissues. The haemoglobin test measures the concentration of this protein in whole blood and is a key marker of red cell mass and oxygen-carrying capacity.

HbA (hemoglobin A) is the major adult hemoglobin molecule composed of two alpha and two beta globin chains (α2β2). The hemoglobin electrophoresis test measures the proportion of different hemoglobin types (HbA, HbA2, HbF, and abnormal variants like HbS or HbC) in blood.

HbA1c (glycosylated haemoglobin) is haemoglobin with glucose irreversibly attached; the test measures the percent of haemoglobin that is glycated and reflects average blood glucose over the prior 8–12 weeks. It is used to detect and monitor diabetes mellitus and to assess long‑term glycaemic control.

Hemoglobin A2 (HbA2) is a minor adult hemoglobin composed of two alpha and two delta globin chains (α2δ2). The HbA2 test measures the percentage of total hemoglobin made up by HbA2, typically by hemoglobin electrophoresis or high-performance liquid chromatography.

Hemoglobin C (HbC) is an inherited variant of the beta-globin chain caused by a single amino-acid substitution (glutamic acid → lysine at position 6). The hemoglobin electrophoresis test measures the proportion of different hemoglobin types (HbA, HbA2, HbF, HbS, HbC, etc.) in blood and detects variants like HbC.

HbF (fetal hemoglobin) is the form of hemoglobin normally produced before birth (alpha2-gamma2). The HbF test measures the proportion of total hemoglobin made up by fetal hemoglobin, usually by hemoglobin electrophoresis or HPLC.

Hemoglobin S (HbS) is an abnormal variant of the β‑globin chain caused by a single amino‑acid substitution; it polymerizes under low-oxygen conditions, deforming red cells into the characteristic “sickle” shape. The HbS measurement (usually reported as percent of total hemoglobin on hemoglobin electrophoresis or HPLC) identifies carriers (sickle cell trait) and people with sickle cell disease (homozygous or compound heterozygous states).

The Helicobacter pylori (H. pylori) stool antigen test detects proteins (antigens) from H.

Helicobacter pylori IgG (H. pylori Abs.

Helicobacter pylori Abs. (IgM) measures circulating IgM-class antibodies directed against H.

Herpes Simplex Virus type 2 (HSV-2) IgM is a blood test that detects IgM-class antibodies directed against HSV-2. IgM antibodies typically arise early after infection and are used as a marker of recent or acute infection, most often genital herpes.

Homocysteine is an amino acid produced during methionine metabolism. The blood homocysteine test measures total plasma/serum homocysteine and helps assess risk for vascular disease and thrombotic disorders.

High-sensitivity C‑reactive protein (hsCRP) is a sensitive blood measure of low-grade systemic inflammation. The liver produces CRP in response to cytokines (especially IL‑6) released during tissue injury, infection or chronic inflammatory activity; the high-sensitivity assay detects low CRP concentrations relevant to cardiovascular risk assessment.

Interleukin‑6 (IL‑6) is a pro‑inflammatory cytokine produced by immune cells (macrophages, T cells), endothelial cells and adipocytes. The IL‑6 blood test measures circulating IL‑6 concentration, typically by immunoassay, and reflects activation of the acute‑phase inflammatory response.

Total IgE (immunoglobulin E) is an antibody class produced by B cells that plays a central role in allergic (atopic) reactions and defense against certain parasites. The total IgE blood test measures the overall concentration of IgE in circulation — not specific triggers — and is used to support evaluation of allergic diseases (asthma, allergic rhinitis, atopic dermatitis, food allergy), suspected helminthic (parasitic) infection, or rare immune disorders (e.g., hyper‑IgE syndromes).

Immunoglobulin M (IgM) is a large antibody produced by B cells as the first-line humoral response to a new or recent infection. A serum IgM level measures the concentration of this antibody in blood and helps distinguish acute/recent infection from past exposure (which is often marked by IgG).

Immature granulocytes (IGs) are young forms of neutrophil-line white blood cells (promyelocytes, myelocytes and metamyelocytes) that are normally confined to the bone marrow. The IG count on a complete blood count (CBC) with differential measures the percentage or absolute number of these immature cells in peripheral blood.

Indirect bilirubin (unconjugated bilirubin) is the lipid-soluble form of bilirubin produced when hemoglobin from aging red blood cells is broken down. It circulates bound to albumin and is taken up by the liver for conjugation (making it water-soluble) and excretion.

Fasting insulin measures the concentration of insulin in the blood after an overnight fast and reflects pancreatic beta‑cell secretion of endogenous insulin. The test helps assess how much insulin the body produces at baseline and is used alongside fasting glucose and HbA1c to evaluate insulin resistance, prediabetes, type 2 diabetes risk, metabolic syndrome, and conditions like polycystic ovary syndrome (PCOS).

Insulin is a hormone produced by pancreatic beta cells that helps cells take up glucose from the blood. A "random" insulin test measures circulating insulin at any time (not necessarily fasting) and is used along with blood glucose to evaluate insulin production and regulation.

Serum iron measures the amount of circulating iron bound to transferrin in the blood. It helps evaluate iron status and is used alongside ferritin, total iron‑binding capacity (TIBC) or transferrin saturation to diagnose different types of anemia and iron disorders.

Ketones are small molecules (acetoacetate, beta-hydroxybutyrate, and acetone) produced when the body breaks down fat for energy instead of using glucose. A urine ketone test detects acetoacetate in the urine and indicates increased fat metabolism.

Lactate dehydrogenase (LDH) is an enzyme present in nearly all body tissues (liver, heart, muscle, red blood cells, kidneys, lungs). A serum LDH test measures the total circulating enzyme released when cells are damaged or destroyed.

The LDL:HDL ratio compares the concentration of low‑density lipoprotein cholesterol (LDL, the atherogenic “bad” cholesterol) to high‑density lipoprotein cholesterol (HDL, the protective “good” cholesterol). It is calculated from a fasting or non‑fasting lipid panel and expresses overall atherogenic risk: higher ratios mean more LDL relative to HDL and greater risk of plaque formation and cardiovascular disease (CVD).

Low-density lipoprotein (LDL) cholesterol is the lipoprotein fraction that carries cholesterol from the liver to peripheral tissues. The LDL test measures the concentration of cholesterol within LDL particles, a key driver of plaque formation in arteries (atherosclerosis).

Large Unstained Cells (LUC) is a parameter reported by automated hematology analyzers as part of the complete blood count (CBC) with differential. It represents a small population of white blood cells that are larger than typical lymphocytes and do not take up the usual cytochemical stains or do not fit normal analyzer classification algorithms.

Leukocytes in a urine analysis are white blood cells (WBCs) that indicate inflammation or immune response in the urinary tract. The test measures WBCs either by microscopic counting (WBCs per high-power field) or by a dipstick detecting leukocyte esterase (an enzyme released by WBCs).

Luteinizing hormone (LH) is a glycoprotein hormone produced by the anterior pituitary that regulates reproduction. In people with ovaries, an LH surge triggers ovulation and supports corpus luteum formation and progesterone production; in people with testes, LH stimulates Leydig cells to produce testosterone.

Lipase is a digestive enzyme produced mainly by the pancreas that breaks down dietary fats into absorbable fatty acids and glycerol. A serum lipase test measures the activity of this enzyme in the blood and is used to detect pancreatic injury or inflammation.

Lipoprotein(a) or Lp(a) is a lipoprotein particle similar to LDL but with an added protein called apolipoprotein(a). The Lp(a) test measures the concentration of these particles in blood.

Liquid Based Cytology (LBC) is a method of preparing cells collected from the cervix (via a cervical swab) into a thin, uniform layer on a slide for microscopic examination. The test evaluates cellular changes that may indicate infection, inflammation, precancerous lesions (cervical intraepithelial neoplasia, CIN) or invasive cervical cancer.

Lupus anticoagulant (LA) is not a single molecule but a group of antiphospholipid antibodies that interfere with phospholipid-dependent clotting tests in the laboratory. The test detects these antibodies using clotting assays (eg, dilute Russell viper venom time [dRVVT], and aPTT-based assays) and reports whether an inhibitor consistent with LA is present.

Lymphocytes are a type of white blood cell (WBC) central to the adaptive immune system; major subtypes include B cells (antibody production), T cells (cell‑mediated immunity) and natural killer (NK) cells (innate cytotoxicity). The CBC reports lymphocytes as an absolute count and as a percentage of total WBCs.

Mean Corpuscular Hemoglobin (MCH) is a red blood cell (RBC) index that measures the average amount of hemoglobin contained within a single red blood cell, reported in picograms (pg). It is calculated from hemoglobin and RBC count as part of a complete blood count (CBC) and used to characterize types of anemia.

Mean Corpuscular Hemoglobin Concentration (MCHC) measures the average concentration of haemoglobin inside a red blood cell (RBC). It is calculated from haemoglobin and haematocrit and helps classify anaemias as hypochromic, normochromic or (less commonly) hyperchromic.

Mean corpuscular volume (MCV) is the average volume of a red blood cell (RBC), reported in femtoliters (fL). It is calculated from the hematocrit and red cell count and is used to classify anemias as microcytic, normocytic, or macrocytic.

Mean Platelet Volume (MPV) is a laboratory measurement of the average size of platelets in the blood, reported in femtoliters (fL). It is measured as part of the platelet indices on a complete blood count and reflects platelet production and turnover by the bone marrow.

Malaria (VIVAX) is a laboratory test that detects infection with Plasmodium vivax, a species of malaria parasite that infects red blood cells and can form dormant liver stages (hypnozoites) causing relapses. The test may detect parasites directly (microscopy, antigen-based rapid diagnostic tests, or PCR) or detect specific parasite nucleic acid/protein.

Mean Normal Prothrombic Time (MNPT), commonly reported as Prothrombin Time (PT), measures how long it takes plasma to clot via the extrinsic and common coagulation pathways. The test times activation of clotting factors (particularly VII, X, V, II/prothrombin and fibrinogen).

Metamyelocytes are an immature stage of neutrophil development found in the bone marrow between the myelocyte and band cell stages. The test looks for metamyelocytes on a peripheral blood smear or as part of an automated immature granulocyte count, and it detects abnormal release of marrow precursors into the bloodstream (“left shift”).

Microalbumin refers to small amounts of the blood protein albumin in urine that are below the detection limit of routine dipstick tests but detectable by sensitive assays. The test typically measures urine albumin excretion either as a spot urine albumin-to-creatinine ratio (ACR) or as total albumin excreted over 24 hours.

Monocytes are a type of white blood cell (leukocyte) produced in the bone marrow that circulate in blood and migrate into tissues to become macrophages and dendritic cells. A monocyte count measures the absolute number or proportion of monocytes among total white blood cells.

Neutrophils are a type of white blood cell (granulocyte) that provide first-line defense against bacteria and fungi by ingesting and killing microbes. The neutrophil count (reported as a percentage of white blood cells and as the absolute neutrophil count, ANC) measures the number available to fight infection.

Nitrite in a urine analysis detects nitrite produced when certain bacteria (typically gram-negative enteric organisms such as E. coli) reduce dietary nitrate in the bladder.

Non‑HDL cholesterol is the total cholesterol content of all atherogenic (blood vessel–clogging) lipoproteins: total cholesterol minus HDL‑cholesterol. The test measures the combined cholesterol carried by LDL, VLDL, IDL, lipoprotein(a) and chylomicron remnants — particles linked to atherosclerosis and cardiovascular disease.

Nucleated red blood cells (NRBCs) are immature erythroid precursors that normally mature in the bone marrow and lose their nucleus before entering the peripheral blood as mature red blood cells. A laboratory test for NRBCs counts these immature cells in a peripheral blood smear or reports an absolute NRBC count on an automated CBC with differential.

"Other compounds in urine" refers to a group of non-routine or miscellaneous substances detected on a urinalysis beyond basic measurements (pH, specific gravity, protein, glucose). Commonly screened items include bilirubin, urobilinogen, nitrite, leukocyte esterase, ketones, blood/hemoglobin/myoglobin, and drug metabolites or unusual crystals.

P-LCR (Platelet Large Cell Ratio) is the percentage of circulating platelets that are larger than a defined volume (typically >12 fL) measured by automated haematology analyzers. It is a platelet index that reflects platelet size distribution and production dynamics.

PCT (plateletcrit) is the volume percentage of blood occupied by platelets—analogous to hematocrit for red cells. It is calculated from platelet count and mean platelet volume (MPV) and reflects total circulating platelet mass.

Platelet Distribution Width (PDW) is a measure of the variation in platelet size (anisocytosis) reported as part of a complete blood count or platelet profile. It quantifies how uniform or heterogeneous platelets are; larger variation often indicates increased platelet production or activation.

Prothrombin time (PT) measures how long it takes blood to clot via the extrinsic and common coagulation pathways; "PT (Control)" refers to the reference/control value used to compare a patient’s PT or to calculate ratios/INR. The test detects defects in clotting factors (I, II, V, VII, X) and helps assess liver function, vitamin K status, and the effect of anticoagulants (e.g., warfarin).

Prothrombin Time (PT) measures how long it takes blood plasma to clot by assessing the extrinsic and common coagulation pathways — primarily clotting factors I (fibrinogen), II (prothrombin), V, VII and X. It's used to detect bleeding risk, monitor anticoagulant therapy (especially warfarin), and evaluate liver synthetic function or vitamin K status.

The PT ratio (prothrombin time ratio) is a measure of blood clotting that compares a patient’s prothrombin time to a laboratory control. It reflects function of the extrinsic and common coagulation pathways (factors I, II, V, VII and X) and is used to assess bleeding risk and monitor anticoagulation.

Prothrombin time–International Normalized Ratio (PT‑INR) is a standardized measure of how long blood takes to clot via the extrinsic coagulation pathway. The laboratory reports prothrombin time (PT) adjusted to an INR to allow comparison between labs.

Partial Thromboplastin Time (PTT; often reported as activated PTT or aPTT and sometimes shown with a "control" reference) measures the time it takes plasma to form a clot after activation of the intrinsic and common coagulation pathways. The test evaluates function of factors XII, XI, IX, VIII, X, V, II (prothrombin) and fibrinogen, and is used to detect bleeding disorders (e.g., hemophilia, von Willebrand disease), monitor anticoagulation with unfractionated heparin, and screen for acquired defects such as liver disease, vitamin K deficiency, or disseminated intravascular coagulation.

A peripheral blood smear (peripheral smear) is a microscopic examination of a thin film of blood on a glass slide stained to show red blood cells (RBCs), white blood cells (WBCs) and platelets. The test evaluates cell size, shape, color, inclusion bodies, differential WBC morphology and platelet appearance—information not apparent from automated counts.

Platelet count measures the number of platelets (thrombocytes) in a volume of blood. Platelets are small cell fragments produced by bone marrow that are essential for blood clotting and stopping bleeding.

The serum pregnancy test measures human chorionic gonadotropin (hCG), a hormone produced by the placenta’s syncytiotrophoblast cells shortly after embryo implantation. A serum assay can be qualitative (positive/negative) or quantitative (beta-hCG level in mIU/mL) and detects pregnancy earlier and more precisely than urine tests.

The primary smear of semen is a rapid microscopic screening test prepared from an ejaculate to assess the immediate presence, concentration estimate and gross quality of spermatozoa, basic motility and contamination (white cells, debris). It is a frontline part of semen analysis used in fertility evaluation to detect male-factor infertility (e.g., azoospermia, oligozoospermia, asthenozoospermia, teratozoospermia) and signs of infection or inflammation.

Pro‑myelocytes (promyelocytes) are an early stage in granulocyte development found normally in the bone marrow as immature precursors between myeloblasts and myelocytes. A CBC with peripheral blood smear can detect their presence in circulating blood; ordinarily they are absent from peripheral blood.

Progesterone is a steroid hormone produced mainly by the corpus luteum after ovulation and by the placenta during pregnancy; small amounts are also made by the adrenal glands and testes. The blood test measures circulating progesterone to assess whether ovulation has occurred, to evaluate luteal phase adequacy, and to monitor early pregnancy viability or luteal support during fertility treatment.

Prolactin is a hormone produced by the anterior pituitary that primarily stimulates breast development and milk production (lactation). A prolactin blood test measures the circulating concentration of this hormone.

Free Prostate-Specific Antigen (free PSA or fPSA) is the fraction of PSA circulating in blood that is not bound to plasma proteins. The test measures the unbound PSA level and is interpreted together with total PSA to help distinguish benign prostate conditions (like benign prostatic hyperplasia or prostatitis) from prostate cancer.

Prostate-Specific Antigen (total PSA) is a protein produced by prostate gland cells and released into the blood. The total PSA test measures the combined amount of bound and free PSA in serum.

Protein in a urine analysis refers mainly to albumin and other proteins that appear in the urine when the kidney’s filtration barrier (glomeruli and tubular reabsorption) is impaired or overwhelmed. The test measures the amount of protein excreted in urine—either by a dipstick (qualitative) or by quantitative measurements such as a spot albumin-to-creatinine ratio (ACR) or 24-hour urine protein.

Total protein measures the combined concentration of albumin and globulins in blood. Albumin is mainly made by the liver and maintains oncotic pressure and transports substances; globulins include antibodies and other carrier and inflammatory proteins.

Pus cells in urine are white blood cells (primarily neutrophils) shed into the urinary tract in response to infection or inflammation. The urine microscopy (or automated cell count) quantifies these cells; a positive dipstick leukocyte esterase suggests their presence.

Rheumatoid factor (RF) quantitative measures the concentration of autoantibodies—most commonly IgM antibodies directed against the Fc portion of IgG—in the blood. RF is used to help identify autoimmune inflammatory arthritis, most notably rheumatoid arthritis (RA), and can be positive in other autoimmune diseases (e.g., Sjögren’s), some chronic infections, and certain malignancies.

The RBC (red blood cell) count measures the number of red blood cells in a given volume of blood. Red blood cells contain hemoglobin and transport oxygen from the lungs to tissues and carbon dioxide back to the lungs.

Red cell distribution width (RDW) is a laboratory measure of the variation (anisocytosis) in red blood cell (RBC) size. It is calculated from the red cell histogram on a complete blood count (CBC) and reported as RDW‑CV (%) and/or RDW‑SD (fL).

Red cell distribution width — coefficient of variation (RDW-CV) is a measure of the variation in size (volume) of circulating red blood cells (anisocytosis). It is calculated from the red cell histogram of a complete blood count (CBC) and expressed as a percentage.

RDW-SD (red cell distribution width — standard deviation) is a laboratory measure of the actual width of the red blood cell (RBC) size distribution curve, reported in femtolitres (fL). It quantifies anisocytosis — variability in RBC sizes — and is reported as part of a complete blood count/anemia profile.

Reticulocytes are immature red blood cells recently released from the bone marrow into circulation. The reticulocyte count measures the proportion or absolute number of these cells and indicates how actively the marrow is producing red cells.

The Rh factor (Rhesus D antigen) is a protein on the surface of red blood cells; the Rh test determines whether the D antigen is present (Rh‑positive) or absent (Rh‑negative). It is a categorical blood‑typing test used for transfusion compatibility, prenatal care, and investigation of hemolytic disease of the newborn (HDN).

Rubella IgG measures the concentration of IgG antibodies directed against rubella (German measles) virus in blood. IgG appears after infection or vaccination and generally indicates past exposure and immunity; it does not diagnose acute infection (that requires IgM or PCR).

Rubella Ab IgM is a blood test that detects rubella-specific IgM antibodies produced early in response to rubella virus infection. The test measures recent or active infection (primary or reinfection) rather than long-term immunity, which is assessed by IgG.

Alanine aminotransferase (ALT, historically labeled SGPT) is an enzyme concentrated in liver cells that helps metabolize amino acids. The ALT blood test measures how much of this enzyme is released into the bloodstream — a marker of hepatocellular (liver cell) injury.

Aspartate aminotransferase (AST, also called SGOT) is an enzyme present in liver cells and many other tissues (heart, skeletal muscle, kidney, brain, red blood cells). The blood AST test measures enzyme activity released into circulation when cells are damaged.

Alanine aminotransferase (ALT), often reported as SGPT, is an enzyme found mainly in liver cells that helps convert amino acids during metabolism. The blood ALT test measures the enzyme released into circulation when liver cells are damaged.

The spot urine protein-to-creatinine ratio (PCR) measures the amount of protein in a single urine sample normalized to urine creatinine to estimate daily protein loss without a 24-hour collection. It helps detect and quantify proteinuria from kidney damage (glomerular or tubular), systemic diseases (diabetes, hypertension, autoimmune disease), or transient causes (fever, exercise).

"Semen Type" in a fertility profile refers to the categorical classification of an ejaculate based on standard semen analysis parameters (volume, sperm concentration, total count, motility, morphology and presence of white cells). The test measures sperm number, movement and shape along with semen volume and signs of infection or obstruction.

Serum creatinine measures the amount of creatinine — a waste product of normal muscle metabolism — circulating in the blood. It is filtered and excreted by the kidneys, so blood creatinine is a core marker of kidney filtration (glomerular) function.

Serum folate measures the circulating level of folate (vitamin B9) in blood and reflects recent dietary intake. Folate is essential for DNA synthesis, red blood cell production, and homocysteine metabolism.

The Sickle Cell Solubility Test (and the related sickling phenomenon observation) is a screening method to detect hemoglobin S (HbS), the abnormal hemoglobin responsible for sickle cell trait and sickle cell disease. The solubility test detects insoluble deoxygenated HbS by producing turbidity in a reducing solution; a separate “sickling” test shows red blood cells taking a crescent shape under low-oxygen conditions on a blood smear.

Specific gravity (SG) of urine measures how concentrated or dilute urine is by comparing its density to pure water. It reflects the kidney’s ability to concentrate solutes (electrolytes, urea, glucose, proteins) and helps assess hydration status and renal tubular function.

Triiodothyronine (T3) is one of the two primary thyroid hormones and is the more biologically active form that regulates metabolism, heart rate, temperature, and many cellular processes. The blood test measures either total T3 (T3 bound to transport proteins plus free T3) or free T3 (unbound, active hormone).

T4 (thyroxine) is a primary hormone produced by the thyroid gland; most circulating T4 is protein-bound and serves as a reservoir that is converted peripherally to the more active T3. A T4 blood test measures the amount of thyroxine (usually total T4) in the bloodstream and helps assess thyroid function.

Total Iron Binding Capacity (TIBC) measures the blood’s capacity to bind iron with transferrin, the primary iron-transport protein. The test estimates how much transferrin is available to carry iron and is used with serum iron and ferritin to evaluate iron status.

TPHA (Treponema pallidum hemagglutination assay) is a treponemal serologic test that detects antibodies specific to Treponema pallidum, the bacterium that causes syphilis. The assay measures whether treponemal antibodies are present (usually reported as reactive/positive or non‑reactive/negative).

Thyroid-stimulating hormone (TSH) is a pituitary-produced hormone that regulates the thyroid gland’s production of thyroxine (T4) and triiodothyronine (T3). A TSH blood test measures circulating TSH to assess whether the thyroid is underactive (hypothyroidism) or overactive (hyperthyroidism), or whether pituitary dysfunction is present.

Testosterone is the primary androgen (male sex hormone) produced mainly by the testes in men and by the ovaries and adrenal glands in women. The blood test typically measures total testosterone (bound + unbound) to assess androgen status.

Total bilirubin is the combined measure of unconjugated (indirect) and conjugated (direct) bilirubin in blood. Bilirubin is a breakdown product of heme from red blood cells processed by the liver for excretion in bile.

Total cholesterol is the sum concentration of all cholesterol carried in the blood (including LDL, HDL and VLDL components). The test measures circulating cholesterol, a lipid essential for cell membranes, steroid hormone and bile acid synthesis.

The Total Cholesterol : HDL ratio (TC/HDL ratio) compares the amount of total cholesterol in blood to the "good" cholesterol (HDL). It is a unitless screening marker used to estimate cardiovascular risk: a lower ratio indicates relatively more protective HDL versus total cholesterol, while a higher ratio suggests greater atherogenic burden.

Total Leukocyte Count (TLC), also called the total white blood cell (WBC) count, measures the total number of white blood cells in a volume of blood. White blood cells are key components of the immune system that fight infection and mediate inflammation.

Toxoplasma Ab IgG measures IgG-class antibodies directed against Toxoplasma gondii, the parasite that causes toxoplasmosis. IgG appears weeks after infection and typically persists for life, indicating past exposure or established immunity; it does not by itself prove active recent infection.

Toxoplasma Ab IgM measures IgM-class antibodies directed against Toxoplasma gondii, the parasite that causes toxoplasmosis. IgM antibodies generally appear early after infection and indicate recent or acute exposure.

Serum transferrin is a liver-produced glycoprotein that binds and transports iron in the bloodstream to bone marrow and other tissues. The transferrin test measures the circulating concentration of this carrier protein (not to be confused with transferrin saturation, which is a percent).

Triglycerides are the main form of fat stored and transported in the blood, reflecting circulating fatty acids carried in lipoproteins after meals. The test measures the concentration of triglycerides in plasma, usually after fasting, and helps evaluate lipid metabolism.

Troponin I is a cardiac-specific regulatory protein released into the bloodstream when heart muscle (myocardium) is injured. The troponin I blood test measures the concentration of this protein to detect myocardial injury and quantify its severity.

Typhidot is a rapid serologic test that detects IgM and IgG antibodies directed against a specific outer membrane (50 kDa) antigen of Salmonella enterica serovar Typhi. The test is used to support a presumptive diagnosis of typhoid (enteric) fever by identifying recent (IgM) or past/established (IgG) immune responses.

UIBC (Unsaturated Iron-Binding Capacity) measures the portion of the blood’s iron-binding protein transferrin that is not currently bound to iron — in other words, the reserve capacity available to bind additional iron. It is measured as part of iron studies (with serum iron and TIBC) to evaluate iron status.

Urine spot creatinine is the concentration of creatinine measured in a single (random) urine sample. Creatinine is a breakdown product of muscle creatine and is produced at a relatively constant rate proportional to muscle mass.

Urine spot protein measures the amount of protein present in a single (“spot”) urine sample. It primarily detects albumin and other urinary proteins that normally are retained by the kidneys.

The Urea:Creatinine ratio is a calculated, unitless value comparing blood urea (a waste product of protein metabolism) to serum creatinine (a muscle breakdown product cleared by the kidneys). It helps distinguish causes of elevated nitrogenous wastes (azotemia): a high ratio usually points to prerenal causes (dehydration, low blood flow to the kidney, heart failure, gastrointestinal bleeding, high protein intake or catabolism), whereas a low or normal ratio with rising absolute values suggests intrinsic renal damage (acute tubular necrosis or chronic kidney disease).

The urea breath test (UBT) detects active infection with Helicobacter pylori by measuring labeled carbon dioxide in the breath after ingestion of labeled urea. H.

Uric acid is the end product of purine metabolism produced mainly in the liver and excreted primarily by the kidneys (and partly by the gut). A serum uric acid test measures the concentration of urate in the blood to help evaluate gout, uric acid kidney stones, unexplained renal impairment, and to monitor urate‑lowering therapy.

Urinary calcium measures the amount of calcium excreted in urine (commonly collected over 24 hours or estimated by a spot urine calcium/creatinine ratio). It reflects intestinal absorption, bone turnover and renal handling of calcium.

Urine colour is the visual appearance of freshly voided urine and is recorded as part of a routine urinalysis. It reflects the concentration and chemical composition of urine (primarily urochrome pigment) and can change with hydration status, presence of blood, bilirubin, myoglobin, pigments from foods or drugs, or infection.

Urine beta-hCG (human chorionic gonadotropin) is a pregnancy test that detects hCG hormone excreted in urine after implantation. The test measures presence (qualitative) or, less commonly, concentration (semi-quantitative) of hCG to confirm pregnancy.

Urobilinogen is a colorless byproduct formed in the intestine when gut bacteria reduce bilirubin (the breakdown product of hemoglobin). A small amount is reabsorbed into the bloodstream and excreted in urine; the urine urobilinogen test measures this excreted fraction.

The VDRL (Venereal Disease Research Laboratory) test is a non-treponemal serologic screening test that detects reagin antibodies directed against cardiolipin–lecithin–cholesterol complexes released from damaged host cells and treponemes. It does not detect the organism directly but measures a host antibody response used to screen for syphilis and to monitor treatment response.

Very-low-density lipoprotein (VLDL) is a liver-produced lipoprotein that carries endogenous triglycerides and some cholesterol from the liver to peripheral tissues. A VLDL measurement (usually reported as VLDL–cholesterol or estimated from triglycerides) reflects the triglyceride-rich fraction of blood lipids.

Varicella Zoster Ab IgG measures IgG-class antibodies directed against the varicella‑zoster virus (VZV), the agent that causes chickenpox (varicella) and shingles (herpes zoster). The test determines prior exposure or immunity (natural infection or vaccination) rather than acute infection.

Vitamin A refers mainly to circulating retinol, a fat‑soluble vitamin essential for vision (especially night vision), epithelial integrity, immune function and growth. The blood test measures serum retinol (or retinol-binding protein) to assess body vitamin A status.

Vitamin B1 (thiamine) is a water‑soluble vitamin converted intracellularly to thiamine pyrophosphate (TPP), an essential coenzyme for carbohydrate metabolism (pyruvate dehydrogenase, α‑ketoglutarate dehydrogenase) and the pentose phosphate pathway (transketolase). The laboratory test measures thiamine (often as whole‑blood TPP) or functional status via erythrocyte transketolase activity.

Vitamin B12 (cobalamin) is a water-soluble vitamin essential for DNA synthesis, red blood cell formation, and nervous system myelination. A serum Vitamin B12 test measures the circulating total cobalamin and helps detect deficiency or excess.

Vitamin B2 (riboflavin) is a water‑soluble vitamin essential for energy production, redox reactions and the metabolism of fats, drugs and other vitamins (B6, folate). The test measures riboflavin status indirectly (erythrocyte glutathione reductase activation coefficient, EGRAC) or directly (plasma/serum or RBC riboflavin).

Vitamin B6 refers to a group of chemically related compounds; the biologically active form measured in blood is pyridoxal 5'-phosphate (PLP). The test measures plasma PLP concentration to assess vitamin B6 status.

Vitamin B9 (folate) is a water‑soluble B‑vitamin required for DNA synthesis, cell division and methylation reactions. The laboratory folate test measures circulating folate (usually serum/plasma) and sometimes red blood cell (RBC) folate to assess recent intake and longer‑term stores.

Vitamin C (ascorbic acid) is a water‑soluble vitamin and potent antioxidant required for collagen synthesis, iron absorption, neurotransmitter production, and immune function. The blood (plasma/serum) vitamin C test measures circulating ascorbic acid and reflects recent intake and body stores.

25‑Hydroxyvitamin D (25‑OH D) is the main circulating form of vitamin D and the best indicator of overall vitamin D status. The blood test measures total 25‑OH D (both D2 and D3) to assess adequacy of vitamin D stores used for calcium and phosphorus balance, bone mineralization, and multiple cellular functions.

Vitamin E refers primarily to alpha‑tocopherol, the biologically active, fat‑soluble antioxidant that protects cell membranes from oxidative damage. The serum/plasma alpha‑tocopherol test measures circulating vitamin E levels to assess nutritional status, adequacy of absorption, or excess from supplementation.

Volume in a urine analysis refers to the total amount of urine produced, usually measured as the 24‑hour urine volume. It reflects kidney water handling, fluid intake, and the balance of hormones and solutes that control urine production.

The Widal test (slide method) is a rapid serologic screening test that detects agglutinating antibodies in a patient’s serum against Salmonella enterica serovar Typhi and Paratyphi antigens—primarily O (somatic) and H (flagellar) antigens. It measures whether the patient has circulating anti-Salmonella antibodies that cause visible clumping (agglutination) when mixed with antigen on a slide.

Estimated Average Glucose (eAG) is a calculated value that translates hemoglobin A1c (HbA1c) — the measure of glycation of hemoglobin over the preceding 2–3 months — into the same units used for daily glucose monitoring (mg/dL or mmol/L). It represents an average blood glucose level over time and helps clinicians and patients understand long‑term glycemic control more intuitively.

Urine pH measures the acidity or alkalinity of urine on a scale (lower numbers = more acidic, higher = more alkaline). It reflects renal handling of acid–base balance and can be affected by systemic acid–base disorders, urinary tract infections, and stone-forming risks.