Laboratory investigation of a rare coagulation factor deficiency

Abstract

We present a case report of a 30-year-old pregnant patient who presented for haematologist review following incidental finding of a prolonged APTT. There was no family history of bleeding or thrombosis. Lupus anticoagulant testing, mixing study and factor assays were requested. Laboratory testing revealed a deficiency of prekallikrein. Prekallikrein is a serine protease which forms part of the contact activation phase of coagulation. Prekallikrein deficiency is an autosomal recessive trait, and patients with homozygous or compound heterozygous deficiency will present with plasma prekallikrein levels <1%. While it is understood that patients with prekallikrein deficiency do not have a bleeding tendency, the defect may have a role in the development of hypertension and other cardiovascular conditions. This case study will review the laboratory investigations necessary to diagnose prekallikrein deficiency, and the sensitivity of different APTT reagents to deficiency of prekallikrein.