aPTT (Activated Partial Thromboplastin Time)

Tests the intrinsic clotting pathway — used for heparin monitoring.

What it is

aPTT measures clotting time through the intrinsic pathway, which involves factors VIII, IX, XI, and XII. It is prolonged by heparin anticoagulation, factor deficiencies, and lupus anticoagulant.

Why it matters

Cancer patients requiring anticoagulation with heparin (particularly during hospitalisations or procedures) are monitored using aPTT. It is also prolonged by certain acquired clotting factor deficiencies that can occur in advanced cancer.

How to test

Coagulation panel blood test.

This information is for educational purposes only. Always discuss testing and interpretation of results with your care team.

Optimal range

25–35 seconds. Therapeutic range on heparin: 60–100 seconds.

How often

Twice daily when on IV heparin. Otherwise at each comprehensive panel.