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HIV AB

STDs Biomarker

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Collection Type: Blood

Body System

Related System: STDs

Overview

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 test measures whether HIV-specific antibodies are present, which suggests established infection. It is ordered when there has been possible exposure (unprotected sex, needle sharing), symptoms of acute HIV (fever, sore throat, rash, lymphadenopathy), or for routine screening in pregnancy and high‑risk populations. Antibody appearance varies by time since exposure (usually detectable by 3–12 weeks) and can be affected by age, immune status, pregnancy and recent infections or immunosuppression.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: Included in STD/HIV screening panels (often as part of combined antigen/antibody assays).
Symptoms: Acute viral syndrome (fever, rash, sore throat), unexplained weight loss, persistent infections, swollen lymph nodes.
Diagnoses/monitoring: Detects HIV infection for diagnosis and linkage to care; used in screening pregnant women and blood donors.
Reasons for abnormal (reactive) result: True HIV infection, recent vaccination or infection, autoimmune disease, laboratory cross‑reactivity.
Biological meaning: Reactive indicates presence of HIV antibodies (likely infection); non‑reactive suggests no detectable antibodies or testing during the window period.
Behaviors/family history: Recent high‑risk sexual behavior, shared needles, partner with HIV, or family history of HIV exposure indicate need for testing.

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Understanding Test Results

S/CO 1.0 (Non‑reactive/Negative): No HIV antibodies detected.
Likely no established infection, but if exposure was recent (within previous 3 months, and especially within 2–6 weeks) a false negative due to the window period is possible repeat testing at 4–6 weeks and at 3 months, or perform an HIV RNA (NAT) if very recent exposure is suspected.
S/CO 1.0 (Reactive/Positive): Antibodies detected; suggests HIV infection.
Reactive screening tests require confirmatory testing with an HIV-1/HIV-2 differentiation immunoassay or nucleic acid test (NAT).
A confirmed positive indicates the need for immediate clinical follow‑up, baseline labs and linkage to antiretroviral therapy.
Indeterminate/low‑level reactivity: Borderline S/CO values or discordant results warrant repeat testing and confirmatory differentiation assay or NAT; causes include early seroconversion, cross‑reacting antibodies, recent vaccination, pregnancy or autoimmune conditions.
Clinical action: Any reactive screening result must be confirmed; negative results after potential recent exposure should be followed with repeat testing or NAT to exclude early infection.

Normal Range

Non‑reactive (Negative) Signal‑to‑cutoff (S/CO) 1.0 (no units)

FAQs

Q: What is the meaning of HIV AB?

A: HIV Ab stands for HIV antibodies proteins the immune system makes when infected with HIV-1 or HIV-2. A positive HIV Ab test indicates prior exposure and likely infection, but requires confirmatory testing because false positives can occur. Antibody tests may not detect very recent infections (window period); combined antigen/antibody or nucleic acid tests are used for earlier detection and confirmation.

Q: What is the meaning of HIVAB?

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Q: What is HIV negative?

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Q: What is HIV-1 AB test?

A: The HIV-1 AB test is a blood screening that detects antibodies produced in response to HIV-1 infection. It identifies past or current exposure but may not detect very recent infections during the window period (commonly 3–12 weeks). Reactive results require confirmatory testing (e.g., PCR or supplemental antibody assays). It's used for routine screening, diagnosis, and clinical monitoring.

Q: Can blood type AB positive get HIV?

A: Blood type AB positive does not protect against or increase risk of HIV. HIV transmission depends on exposure to infected blood, semen, vaginal fluids, rectal fluids, or breast milk, and on behaviors (unprotected sex, sharing needles). Blood-type antigens don’t affect HIV entry into CD4 cells. Screened blood supplies, standard precautions, safe sex, needle safety, and testing prevent and detect infection.

Q: How accurate is HIV AB?

A: HIV antibody (Ab) tests are highly accurate after the window period: modern lab ELISA/CMIA and many rapid tests have >99% sensitivity and specificity once antibodies develop (typically 3–12 weeks). Early infection can cause false negatives; nucleic acid tests detect infection earlier. Reactive results require confirmatory testing to rule out rare false positives.