Retrospective examination of coagulation parameters in 33 patients with autoimmune coagulation factor deficiencies in Japan: A single-center analysis.

BACKGROUND:The early diagnosis and prompt treatment of autoimmune coagulation factor deficiencies (AiCFDs) are challenging for physicians when patients present with pseudo-deficiencies or pseudo-inhibitors of multiple coagulation factors. A reason for this is the diagnostic confusion caused by the apparent reduction in coagulation factor activity when using common one-stage coagulation factor measurement assays. METHODS:After confirming the presence of autoantibodies against each coagulation factor, we retrospectively examined the activity of factors X, VIII, and IX (FX, FVIII, and FIX, respectively) and each coagulation factor inhibitor using their chromogenic substrates among 33 patients with AiCFD. RESULTS:Because the apparent coagulation factor deficiency was completely or partially restored in the chromogenic assay, 4, 9, and 22 patients with AiCFD were suspected of having pseudo-FX, pseudo-FVIII, and pseudo-FIX deficiencies, respectively. Moreover, in the chromogenic assay, the specific activities of FX, FVIII, and FIX (determined by their antigen levels) were higher than those in the one-stage assay. The titers for FV inhibitors showed negative correlations with the ratios of FX, FVIII, and FIX activities measured via the one-stage assay and the chromogenic assay. An especially high titer of one coagulation factor inhibitor tends to either cause pseudo-deficiencies or get mistaken for being a pseudo-inhibitor of other coagulation factors. CONCLUSION:Chromogenic assays appear to be superior to conventional one-stage assays when measuring coagulation factor activity in AiCFD cases. Detection of anti-coagulation factor autoantibodies is recommended to avoid overlooking the presence of non-neutralizing autoantibodies.