Division of Blood Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
J Thromb Haemost. 2013 Jul;11(7):1300-9. doi: 10.1111/jth.12259.
Detection and validation of inhibitors (antibodies) to hemophilia treatment products are important for clinical care, evaluation of product safety and assessment of population trends.
Centralized monitoring for factor VIII (FVIII) inhibitors was conducted for patients in the Hemophilia Inhibitor Research Study using a previously reported modified Nijmegen-Bethesda clotting assay (NBA), a chromogenic Bethesda assay (CBA) and a novel fluorescence immunoassay (FLI).
NBA and CBA were performed on 1005 specimens and FLI on 272 specimens. CBA was negative on 880/883 specimens (99.7%) with Nijmegen-Bethesda units (NBU) < 0.5 and positive on 42/42 specimens (100%) with NBU ≥ 2.0 and 43/80 specimens (53.8%) with NBU 0.5-1.9. Among specimens with positive NBA and negative CBA, 58.1% were FLI negative, 12.9% had evidence of lupus anticoagulant, and 35.5% had non-time-dependent inhibition. CBA and FLI were positive on 72.4% and 100% of 1.0-1.9 NBU specimens and 43.1% and 50.0% of 0.5-0.9 NBU specimens. FLI detected antibodies in 98.0% of CBA-positive and 81.6% of NBA-positive specimens (P = 0.004). Among 21 new inhibitors detected by NBA, five (23.8%) with 0.7-1.3 NBU did not react in CBA or FLI. Among previously positive patients with 0.5-1.9 NBU, 7/25 (28%) were not CBA or FLI positive. FLI was positive on 36/169 NBU-negative specimens (21.3%).
FVIII specificity could not be demonstrated by CBA or FLI for 26% of inhibitors of 0.5-1.9 NBU; such results must be interpreted with caution. Low titer inhibitors detected in clot-based assays should always be repeated, with consideration given to evaluating their reactivity with FVIII using more specific assays.
检测和验证血友病治疗产品的抑制剂（抗体）对于临床护理、产品安全性评估和人群趋势评估非常重要。
使用先前报道的改良 Nijmegen-Bethesda 凝血测定法（NBA）、发色底物 Bethesda 测定法（CBA）和新型荧光免疫测定法（FLI），对血友病抑制剂研究中的患者进行集中监测因子 VIII（FVIII）抑制剂。
NBA 和 CBA 分别对 1005 份标本和 FLI 对 272 份标本进行了检测。CBA 在 880/883 份标本（99.7%）中为阴性，Nijmegen-Bethesda 单位（NBU）<0.5，在 42/42 份标本（100%）中为阳性，NBU≥2.0，在 43/80 份标本（53.8%）中为阳性，NBU 为 0.5-1.9。在 NBA 阳性且 CBA 阴性的标本中，58.1%的 FLI 为阴性，12.9%有狼疮抗凝物的证据，35.5%有非时间依赖性抑制。CBA 和 FLI 在 1.0-1.9 NBU 标本中分别有 72.4%和 100%阳性，在 0.5-0.9 NBU 标本中分别有 43.1%和 50.0%阳性。FLI 在 98.0%的 CBA 阳性和 81.6%的 NBA 阳性标本中检测到抗体（P=0.004）。在 21 种由 NBA 检测到的新抑制剂中，有 5 种（23.8%）NBU 为 0.7-1.3，在 CBA 或 FLI 中不反应。在之前 NBU 为 0.5-1.9 的阳性患者中，有 7/25（28%）的患者 CBA 或 FLI 为阴性。FLI 在 36/169 NBU 阴性标本中阳性（21.3%）。
CBA 或 FLI 无法证明 0.5-1.9 NBU 抑制剂中有 26%的 FVIII 特异性；此类结果必须谨慎解释。在基于凝血的检测中检测到的低滴度抑制剂应始终重复检测，并考虑使用更特异的检测方法评估其与 FVIII 的反应性。
