Rapid anti‐HPA‐1a antibody quantification with a Luminex bead‐based assay: A method evaluation

Background and Objectives High concentration of human platelet antigen‐1a (HPA‐1a) antibodies is reported to be associated with severe foetal and neonatal alloimmune thrombocytopaenia (FNAIT). The gold standard for quantification of anti‐HPA‐1a antibodies is the monoclonal antibody immobilization of platelet antigen (MAIPA) assay, which is a laborious method performed in only a few reference laboratories. The aim of this study was to evaluate the performance of the commercially available bead‐based Luminex assay PakLx (Immucor) for quantitative measurement of anti‐HPA‐1a antibodies. Materials and Methods We analysed anti‐HPA‐1a antibody levels in plasma samples from 42 HPA‐1a‐negative women who had given birth to a child with thrombocytopaenia. Quantification of antibodies was performed with two different techniques: MAIPA analysed by spectrophotometry with results expressed in international units (IU)/mL, and PakLx analysed in the Luminex assay with results expressed as the mean fluorescence intensity (MFI). Results In the comparison of the two methods' ability to stratify a result as either positive or negative, PakLx demonstrated 97.6% agreement with the MAIPA assay, with positive and negative predictive values of 96.7% and 100%, respectively. The correlation of the MFI values from PakLx with IU / mL in MAIPA assay was high, with a correlation coefficient ( R 2 ) of 0.92. MFI values were converted into semi‐quantitative results: high, intermediate and low levels of anti‐ HPA ‐1a. Conclusion PakLx shows high agreement with the MAIPA assay and allows fast laboratory turnaround time for the determination of anti‐HPA‐1a antibody levels. The result may be of predictive value in clinical assessments.