Activated Partial Thromboplastin Time (APTT), Plasma

Casandra

Casandra Test Code MC65079Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID APTSCCPT Code 85730

Activated Partial Thromboplastin Time (APTT), Plasma

Clinical Use

Use

The activated partial thromboplastin time (APTT) is used to measure the integrity of the intrinsic and common coagulation pathways, serving as a screening tool for certain coagulation factor deficiencies and abnormalities, such as factors VIII, IX, XI, and XII. It helps detect coagulation inhibitors including lupus anticoagulant and antiphospholipid antibodies. The APTT is also utilized for monitoring unfractionated heparin therapy. It is essential for evaluating a prolonged APTT result to differentiate between coagulation factor deficiencies and inhibitors, especially when used in conjunction with other coagulation tests and clinical data.

Special Instructions

Orderable only as part of a special coagulation profile or reflex testing. Ensure that heparin or Coumadin therapy status is noted. Accurate interpretation often requires additional testing like thrombin time, prothrombin time, and others as part of interpretive panels offered by the Special Coagulation Laboratory.

Limitations

The APTT test does not detect all coagulation inhibitors or lupus anticoagulants and may miss mild coagulation factor deficiencies. Sensitivity to factor deficiencies varies with different reagents. Lipemic specimens can interfere with clot detection. A normal or shortened APTT does not exclude a hemostatic defect, necessitating specific clotting factor assays if bleeding diathesis is clinically suspected. APTT mixing studies are ineffective when APTT is normal.

Test Details

New York Approved