A discrepancy between prothrombin time and Normotest (Hepaplastintest) results is useful for diagnosis of acquired factor V inhibitors

Acquired coagulation factor inhibitors are rare. Among them, coagulation factor V (FV) inhibitor is particularly uncommon and presents with variable clinical manifestations. Certain acquired FV inhibitor patients have only mild bleeding or, in select cases, no symptoms at all, leading to spontaneous recovery. Others have life-threatening bleeding that requires medical attention. Thus, a prompt decision regarding diagnosis and clinical intervention is crucial for such patients. In five acquired FV inhibitor cases treated in our facility, each patient had a malignancy as an underlying disease and all unexpectedly showed prolongation of both prothrombin time (PT) and activated partial thromboplastin time (APTT). They all also displayed a discrepancy between PT and Normotest (Hepaplastintest, HPT) results. All but one patient experienced no bleeding at the time of diagnosis and achieved spontaneous recovery in 1–3 weeks. The patient with bleeding symptoms received plasma exchanges and a platelet transfusion. Useful markers in diagnosing the presence of an acquired FV inhibitor were a sudden prolongation of PT and APTT, and a discrepancy between the PT/APTT and HPT assays. Spontaneous recovery can be expected for patients with only minor bleeding.