This test measures Factor XII, which initiates the intrinsic pathway of coagulation.
Diagnostic Value: Low Factor XII activity prolongs aPTT but typically does not cause bleeding; instead, some studies suggest it may increase thrombosis risk.
Clinical Significance: Helps explain isolated prolonged aPTT and distinguish it from true bleeding disorders.
Symptom Correlation: Usually asymptomatic, though linked to possible thrombotic tendency.
The Factor XII Activity test clarifies unexplained prolonged clotting results and assesses intrinsic pathway function.