Nationwide Survey of Laboratory Practices for Factor VIII Inhibitor Detection in China.

Introduction: The Bethesda assay (BA) and the Nijmegen-Bethesda assay (NBA) are commonly used to measure inhibitors in patients with haemophilia A (HA). The laboratory results of inhibitor assays have been demonstrated to be highly variable.

Aims: To understand the current testing methods used in different laboratories in China and promote improvements in laboratory detection.

Methods: An external quality assurance (EQA) survey of FVIII inhibitor testing was conducted by the Chinese Alliance for Blood Disease and Tianjin Blood Disease Medical Quality Control Centre to evaluate the testing methods used.

Results: Seventy-eight questionnaires and matched EQA responses were received. A total of 94.9% of participating centres reported the use of BA for the FVIII inhibitor assay. Five EQA samples revealed titres and coefficients of variation (CVs) of 0.7 BU/mL (0-1.9 BU/mL; CV = 63.9%), 2.0 BU/mL (0.6-4.8 BU/mL; CV = 40.7%), 5.6 (2.3-11.6 BU/mL, CV = 33.4%), 14.6 (4.8-27.2 BU/mL, CV = 32.8%) and 37.2 (11.5-80.0 BU/mL, CV = 35.2%), respectively. About 37% laboratories failed to detect low-level inhibitors of approximately 1 BU/mL. The overall results of Dade Actin were lower than those of other APTT reagents.

Conclusions: There is a wide variety in the stages of inhibitor testing, and further local standardization is required to improve interlaboratory comparison of factor VIII inhibitor assay.