Recent initiatives from the RCPA haematology QAP: PFA-100 and FVIII inhibitors

Abstract

The PFA-100 is commonly used in haemostasis laboratories for screening and monitoring of both von Willebrand disease (VWD) and platelet dysfunction. Testing requires fresh whole blood, so providing an external quality assurance (EQA) sample is a challenge and no EQA can currently provide such material. The Royal College of Pathologists of Australasia (RCPA) Haematology Quality Assurance Program (QAP) has recently sent two trial surveys to establish the feasibility of providing an EQA program for the PFA-100. The results from the trials were encouraging and will provide the basis for formulating an external EQA program. The factor inhibitors most commonly seen by laboratories are those directed against factor VIII (FVIII), and most usually detected either using Bethesda assays or Nijmegen modified methods. Inter-laboratory evaluations, including those recently conducted by the RCPA Haematology QAP, have consistently shown high variability in laboratory results for inhibitor assays, as well as false positive and negative identification. In brief, we recently conducted two questionnaire-based surveys and two wet-challenge surveys and identified ongoing high inter-laboratory variation, with CVs around 50% not uncommon, and that some 15% of Bethesda testing laboratories fail to detect low-level inhibitors of around 1 BU/mL. In conclusion, our experience indicates that is still much need for standardisation and improvement in factor inhibitor detection and the performance of PFA-100 screening, and we hope that the two new modules offered from 2010 provide a basis for future improvements in these areas.