Factor Inhibitor Testing: An Update from Australasia/Asia-Pacific

Area of Science:

• Hematology
• Immunology
• Clinical Pathology

Background:

• Factor VIII (FVIII) inhibitors are antibodies targeting coagulation FVIII, reducing its activity.
• These inhibitors can arise in congenital hemophilia A (allo-antibodies) or acquired hemophilia A (auto-antibodies).
• Accurate FVIII inhibitor testing is crucial for patient management.

Purpose of the Study:

• To evaluate the quality of FVIII inhibitor testing in a specific geographic region.
• To analyze recent external quality assessment (EQA) data from 2020-2024.
• To identify trends and potential areas for improvement in FVIII inhibitor diagnostics.

Main Methods:

• Utilized data from the Royal College of Pathologists of Australasia Quality Assurance Program (RCPAQAP) FVIII inhibitor module.
• Analyzed results from over 80 participating laboratories over a 5-year period.
• Assessed performance based on the correct detection/non-detection of FVIII inhibitors in proficiency testing samples.

Main Results:

• >99% of participants correctly identified the presence or absence of FVIII inhibitors.
• Most interpretation errors were attributed to transcription or data entry, not analytical failures.
• Moderate coefficients of variation (25-40%) were observed for FVIII inhibitor titers, regardless of method (Bethesda vs. Nijmegen).

Conclusions:

• Laboratories demonstrate high proficiency in detecting FVIII inhibitors.
• Focus should be placed on minimizing data transcription and entry errors.
• While detection is accurate, variability in reported inhibitor titers warrants attention.