The new approach of laboratory diagnosis for a patient with acquired factor XI deficiency with high titer auto-antibodies by combination use of synthetic chromogenic substrate assay for factor VIII and factor IX

Abstract

We have analyzed a female patient who expressed recurrent spontaneous bleeding in her age 40s with an obvious APTT prolongation. However, her diagnosis had difficulties due to her complicated laboratory results. Her laboratory tests showed a significant reduction of all intrinsic coagulation factors (factors VIII, IX, XI, and XII), and the presence of high titer antibodies to factor XI was presumed by the results of the crossing mixing test, the coagulation factor assays with multi-diluted samples, the immunological methods and the synthetic chromogenic substrate methods. The immunological analysis which use IgG purified from patient plasma was confused due to the strong affinity of IgG and factor XI. However, it was revealed that the antibody was directed against factor XI by combination use of chromogenic substrate assay for factor VIII and factor IX. There are only a limited number of reports of such cases, and the results of coagulation factor level often become false values which are interfered by high titer inhibitor. It is very important to properly grasp the disease state from multiple distinct analyses.