市售不同原理之第八因子活性分析方法學應用於Emicizumab治療之嚴重A型血友病病患之診斷與監控

Application of Different Commercial Products for Factor VIII Activity Determination in Severe Hemophilia A Patients with Emicizumab Therapy

Emicizumab 是一種人源化的雙特異性抗體，作用機轉為模擬活化態的第八凝血因子 (FVIIIa) 功能，對於已產生FVIII抗體的嚴重型A型血友病患一大福音。本次實驗目的為收集施打 Emicizumab 病患的臨床血漿檢體，比較三種不同原理之第八因子活性方法，找出合適檢驗方法。利用三種FVIII檢驗驗方法分析正常人檢體，三種方法間無統計上的差異。六位使用 Emicizumab 藥物的病患，用藥後的 aPTT 秒數大幅縮短平均為21.5秒。FVIII活性檢測部分，以 aPTT 為基質的凝固法FVIII活性可高達250%-750%，明顯有偽性上升。若以人源性呈色法檢驗分析，獲得到的FVIII平均活性有12.2%活性，而使用牛源性呈色法檢測，則FVIII活性均<1%。在FVIII抗體檢測部分，aPTT 為基質的凝固法檢測不到病人本身存在的FVIII抗體，人源性呈色法FVIII抗體結果3位陰性及3位陽性，牛源性呈色法FVIII抗體結果六位病患檢驗結果為陽性。綜合上述實驗結果，在臨床上進行 Emicizumab 治療的A型血友病病患的臨床血液凝固相關檢驗，必須選擇正確檢驗方法，才能提供給臨床醫師正確的數據做為病人的診斷依據。

Emicizumab is a humanized bispecific antibody to mimic the function of FVIIIa. It provides great benefits for the hemophilia patients with FVIII inhibitor. In this study, we attempted to compare the clinical applications in three kinds of FVIII activity determination kits. In normal individuals, no significantly different results were observed among three FVIII activity determination methods. In six Emicizumab treated patients, their aPTT is significantly shortened to an average of 21.5 seconds. FVIII activities were overestimated by using aPTT based clotting methods, ranging from 250%-750%. The average FVIII activity measured by human or bovine derived FVIII chromogenic method was 12.2% and <1%, respectively. The FVIII inhibitor titers were undetectable by using aPTT-based clotting assay. Three positive and three negative results of FVIII inhibitor titer were observed by the determination of human derived FVIII chromogenic method. In contrast, bovine-derived chromogenic assay provides all positive results of FVIII inhibitor titer from six Emicizumab patients. In conclusion, we should notice the clinical interpretation and the possible interference on each test report especially in the hemophilia A patient with Emicizumab therapy. Therefore, we can provide correct results to clinicians for proper diagnosis of patients.