Key Takeaways

An elevated activated partial thromboplastin time (aPTT) and normal prothrombin time (PT) suggests a deficiency of or inhibitor against a clotting factor(s) in the intrinsic pathway.

Correction of a prolonged aPTT with normal plasma (mixing study) suggests a deficiency in a clotting factor(s) rather than an inhibitor.

Deficiency in factor VIII (FVIII) may be congenital (hemophilia A or von Willebrand disease) or acquired (typically acquired von Willebrand syndrome [AVWS]).

von Willebrand disease – whether congenital or acquired – is confirmed by demonstrating reduced von Willebrand factor (vWF) activity.

vWF activity that is disproportionately low relative to reduction in vWF antigen suggests loss of high molecular weight vWF antigens, as seen in von Willebrand disease, type 2 or AVWS.

AVWS is almost always associated with an identifiable medical condition such as a plasma cell dyscrasia, cardiac condition, medication effect, or autoimmune disorder.

Treatment of AVWS involves treating bleeding (using DDAVP and/or vWF/FVIII concentrates) and treating the underlying medical condition.