Fukutake Katsuyuki, Kobayashi Tomomi, Sommer Jurg M, Hirakata Toshiyuki
Department of Laboratory Medicine, Tokyo Medical University, Tokyo, Japan.
Department of Molecular Genetics of Coagulation Disorders, Tokyo Medical University, Tokyo, Japan.
Int J Lab Hematol. 2020 Apr;42(2):162-169. doi: 10.1111/ijlh.13133. Epub 2019 Dec 10.
The one-stage clotting assay is used to measure factor IX (FIX) activity in patients' plasma samples and in FIX products for hemophilia treatment. However, the diversity of reagents and instruments has resulted in significant FIX assay variability.
The accuracy of the one-stage clotting assay to measure recombinant FIX Fc fusion protein (rFIXFc) activity was evaluated by major Japanese hemophilia treatment centers and commercial laboratories that measure factor IX activity for a majority of hemophilia B patients in Japan. Plasma-derived FIX (pdFIX) and recombinant FIX (rFIX) products were used as comparators. FIX-deficient plasma was spiked with four levels of FIX products based on label potency and measured under blinded conditions by routine one-stage clotting assay procedures in 19 participating laboratories. Interlaboratory coefficient of variation and spike recovery were calculated.
Interlaboratory coefficient of variation of rFIXFc was not significantly different from that of rFIX, but appeared larger than that of pdFIX. Mean spike recovery for rFIXFc was generally comparable to rFIX and pdFIX. However, larger discrepancies between pdFIX and rFIX were observed in three of nine laboratories using ellagic acid-based activated partial thromboplastin time reagents.
Recombinant FIX Fc fusion protein activity was found to be similar to that of rFIX or pdFIX by the one-stage clotting assay. However, minimizing interlaboratory variability is vital for optimizing future patient care.
一步凝血试验用于测量患者血浆样本以及用于血友病治疗的FIX产品中的凝血因子IX（FIX）活性。然而，试剂和仪器的多样性导致FIX检测存在显著差异。
日本主要的血友病治疗中心和商业实验室对一步凝血试验测量重组FIX Fc融合蛋白（rFIXFc）活性的准确性进行了评估，这些实验室为日本大多数B型血友病患者测量凝血因子IX活性。以血浆源性FIX（pdFIX）和重组FIX（rFIX）产品作为对照。将FIX缺乏的血浆与基于标签效价的四种水平的FIX产品混合，并在19个参与实验室中通过常规一步凝血试验程序在盲法条件下进行测量。计算实验室间变异系数和加标回收率。
rFIXFc的实验室间变异系数与rFIX的变异系数无显著差异，但似乎大于pdFIX的变异系数。rFIXFc的平均加标回收率通常与rFIX和pdFIX相当。然而，在使用基于鞣花酸的活化部分凝血活酶时间试剂的9个实验室中的3个实验室中，观察到pdFIX和rFIX之间存在较大差异。
通过一步凝血试验发现重组FIX Fc融合蛋白活性与rFIX或pdFIX的活性相似。然而，最大限度地减少实验室间变异对于优化未来患者护理至关重要。
