エミシズマブ治療患者における血液凝固波形分析を用いた自己免疫性FVIII阻害因子の評価

Background/Objectives: Autoimmune factor VIII deficiency (AiFVIIID) is a rare disorder that causes severe bleeding. Emicizumab has recently been found to be effective in treating AiFVIIID; however, monitoring with standard coagulation tests presents challenges. Methods: Clot waveform analysis (CWA), which involves CWA-activated partial thromboplastin time (APTT), the CWA-small amount of tissue factor activation assay (sTF/FIXa), and clotting time using a small amount of thrombin (sTT), was used to both diagnose AiFVIIID and monitor emicizumab. Results: CWA-sTT reflects the residual FVIII activity in patients with AiFVIIID. Several tests were employed, including APTT, FVIII activity, CWA, mixing tests with normal plasma, FVIII inhibitor assays, and anti-FVIII antibody activity for the diagnosis of AiFVIID in three cases. However, the sensitivity of APTT reagents to AiFVIID differed between thrombocheck-APTT and APTT-SP. Emicizumab treatment was effective for major bleeding, and anti-FVIII antibody activity could be measured using CWA-sTT. Conclusions: The sensitivity of APTT reagents to AiFVIID varies. CWA-sTT may provide utility in the diagnosis of AiFVIIID. Emicizumab is useful for the treatment of AiFVIID, and anti-FVIII antibody activity can be measured even in patients treated with emicizumab.