Test guide
Activated Partial Thromboplastin Time (APTT)
A clotting test of the intrinsic and common pathways, used to monitor unfractionated heparin and investigate prolonged bleeding histories.
What it is for
Monitors unfractionated heparin therapy, screens for intrinsic-pathway factor deficiencies (including haemophilia A and B), detects lupus anticoagulant in combination with mixing studies, and supports pre-procedure bleeding-risk assessment.
Limitations
Sensitive to pre-analytical variation (under-filled tubes, delayed processing, heparin contamination). Does not reflect direct oral anticoagulant effect reliably. A lupus anticoagulant can prolong APTT without increasing bleeding risk — interpretation requires the clinical context and mixing studies.
Before you test
Note any anticoagulant therapy before the test. Tubes must be filled completely and processed promptly.
Health information only. This guide does not diagnose or replace advice from a healthcare professional.
Also known as
- APTT
- aPTT
- PTT
Reviewed products
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