A case of autoimmune-acquired coagulation factor V deficiency where cross mixing test with adding another dilution series was useful for diagnosis

Abstract

Autoimmune-acquired coagulation factor V deficiency (AiFVD), which is associated with autoantibodies against factor V, presents with a wide range of symptoms. We have encountered a unique case of AiFVD exhibiting thrombosis. Conventional cross mixing test (CMT) could not reveal the presence of “inhibitor pattern”. However, the modified CMT, in which we added increased dilution ratio series, indicated the “inhibitor pattern” more clearly, and suggested a diagnosis of AiFVD. To exam adequately (avoiding conducting tests for lupus anticoagulant for all suspected cases), we should perform CMT on the patient with prolonged PT or APTT within the day within the hospital. In the present case, numerization of the data with adding another dilution series can take us to the accurate diagnosis. Such approach offers the additional benefit of being less dependent on laboratories skills or experience, and of simultaneously enhancing objectivity in the data obtained.