Home Biomarkers Partial Thromboplastin Time(Control)

Partial Thromboplastin Time(Control)

CBC Biomarker

Sample Needed

Collection Type: Blood

Body System

Related System: CBC

Overview

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. Symptoms prompting the test include unusual bleeding, easy bruising, prolonged bleeding after injury/surgery, or unexplained thrombosis. Newborns normally have longer PTTs; pregnancy and some hormonal states may shorten PTT; values can vary by age, assay reagent, and lab-specific controls.

People also test for

Test Preparation

Fasting not required, avoid certain medications if advised

Why Do I Need This Test

Profile: often ordered alongside coagulation panels (frequently grouped with CBC or clotting profile).
Symptoms: unexplained bleeding, heavy menstrual bleeding, excessive bruising, or thrombosis history.
Diagnoses/monitoring: bleeding disorders, liver disease, DIC, heparin therapy monitoring, lupus anticoagulant.
Reasons for abnormal levels: factor deficiencies, anticoagulant drugs (heparin), liver dysfunction, inhibitors (e.g., lupus anticoagulant).
Biological meaning: prolonged PTT = impaired intrinsic/common pathway or anticoagulant effect; shortened PTT = possible hypercoagulable state.
Lifestyle/family: heavy alcohol use, certain supplements/drugs, and family history of hemophilia or clotting disorders warrant testing.

Run our symptom checker to see if this test is right for you

Symptom Checker

Understanding Test Results

Values within 25–40 seconds are considered normal for most adult laboratories.
Mildly prolonged results (about 40–60 seconds) may indicate partial factor deficiencies, early liver disease, low fibrinogen, presence of anticoagulants (therapeutic heparin), or inhibitors such as lupus anticoagulant; correlation with clinical history and repeat testing or mixing studies is needed.
Moderately prolonged values (≈60–90 seconds) suggest significant factor deficiency, high-dose anticoagulation, or active disseminated intravascular coagulation and usually require prompt evaluation.
Severe prolongation (>90 seconds) is associated with major clotting factor deficits, severe liver failure, or massive anticoagulation and carries high bleeding risk.
Shortened values (<25 seconds) can be seen with a hypercoagulable state (elevated factor VIII or fibrinogen, pregnancy, oral contraceptives) and may be associated with increased thrombotic risk.
Therapeutic heparin is typically monitored to achieve an aPTT of roughly 1.5–2.5 times the control value; exact targets depend on institutional protocols.
Interpretation must consider age (neonates normally have higher PTTs), recent medications, and assay-specific controls.

Normal Range

25-40 seconds

FAQs

Q: What is the control time for PTT?

A: The control (normal) partial thromboplastin time (PTT/aPTT) is typically about 25–40 seconds, though exact ranges vary by laboratory and reagent. For unfractionated heparin therapy the therapeutic target is usually 1.5–2.5 times control (roughly 45–70 seconds). Always use the reference range provided by the performing laboratory when interpreting results.

Q: What is control in aPTT?

A: In aPTT testing, a control is a plasma sample with a known clotting time run alongside patient specimens to verify assay accuracy. Laboratories use normal and abnormal controls to confirm reagents, instrument performance, and technique. Controls must fall within established ranges before releasing patient results; deviations prompt repeat testing, reagent checks, or instrument maintenance and help monitor anticoagulation like heparin.

Q: What does it mean if PTT is high?

A: A high PTT (partial thromboplastin time) means blood takes longer than normal to clot. It points to intrinsic pathway problems—factor deficiencies (e.g., hemophilia), anticoagulant use (heparin), liver disease, consumptive conditions (DIC), or interfering antibodies such as lupus anticoagulant. Clinically it often indicates increased bleeding risk but requires further testing to identify the cause and guide treatment.

Q: What's the difference between PTT and aPTT?

A: PTT (partial thromboplastin time) and aPTT (activated PTT) assess the intrinsic and common coagulation pathways. PTT was the older, less standardized method; aPTT adds an activator (e.g., kaolin) to start clotting and standardize the test, giving more reliable results. Both evaluate factors XII, XI, IX, VIII and are used to screen bleeding disorders and monitor unfractionated heparin.

Q: How to manage prolonged aPTT?

A: Manage prolonged aPTT by repeating the test and reviewing medications (heparin, DOACs). Assess bleeding vs thrombosis, check CBC, liver function and DIC screen. Do a mixing study to separate factor deficiency from inhibitor, then perform specific factor assays and lupus anticoagulant testing. Treat the cause: stop offending drugs, give protamine for heparin, use factor concentrates/FFP or cryoprecipitate if bleeding, and consult hematology.

Q: What is a normal PTT and aPTT time?

A: Normal activated partial thromboplastin time (aPTT) is about 25–40 seconds (commonly 30–40 s). Partial thromboplastin time (PTT, unactivated) is longer, typically around 60–90 seconds depending on the laboratory. Reference ranges vary by assay and lab; results should be interpreted using your local lab’s reference interval and clinical context. If values are abnormal, consult a clinician for further testing.