Evaluation of the suitability of the World Health Organization International Reference Reagent for Hb A₂ quantitation (89/666) for continued use

Abstract

Introduction The accurate determination of Hb A2 is a key marker when screening for a β‐thalassaemia carrier. Data from external quality assessment (EQA) exercises have shown a lack of alignment of Hb A2 quantitation both within and between methods. The only reference material available for Hb A2 quantitative assay at the time of writing is the World Health Organization International Reference Reagent (89/666; WHO IRR) prepared in the 1980s and not validated for all current methodologies. Method The WHO IRR was analysed for Hb A2 concentration by 52 laboratories using a representative range of high‐performance liquid chromatography and capillary electrophoresis analysers. The results of the analysis were compared to those of a whole blood EQA specimen of similar Hb A2 concentration, distributed in the same week. Results The mean Hb A2 value obtained for the WHO IRR was 5.17%, compared to the assigned value of 5.3%. The range of results returned was wide (4.0%‐6.2%), with differences in the results observed by between and within analyser groups. A similar range of results was seen with the whole blood sample, although the bias observed between analyser types was different from that seen with the WHO IRR. Conclusion The results may indicate a lack of commutability of the WHO IRR material, resulting from deterioration, matrix effects or changes in reagent formulation or calibration parameters. Further examination of the suitability of the WHO IRR (89/666) for continued use is required.

Further evaluation of the world health organization international reference reagent for Haemoglobin A2 measurement

“…The purpose of this study was to further investigate the suitability of the WHO IRR for HbA 2 for its continued use, a preliminary study having been undertaken by UK NEQAS in 2015 4 . In the 2015 study, participating laboratories were all based in the UK and the comparison of results from whole blood specimens to the lyophilized IRR was restricted to a single β‐thalassaemia whole blood specimen.…”

“…A study was undertaken in 2015 by UK NEQAS Haematology 4 in which an ampoule of the WHO IRR was circulated to each of 52 UK laboratories for HbA 2 estimation using their usual analytical procedures. The results indicated that the overall performance of the IRR was good and that no significant degradation had occurred in the product.…”