P139 HLA antibody identification by Luminex single antigen – Interlaboratory comparison

Abstract

Aim Single antigen bead (SAB) assays are widely used for histocompatibility testing to detect and measure the strength of HLA antibodies. The aim of this study is to compare the SAB data among labs to examine variability in antibody reporting. Methods Labs participating in the UCLA Flow and Virtual Crossmatch Exchange tested sera with a broad range of class I and/or class II specificities. The study collected and analyzed Luminex SAB data reported by participants from 4 sera sent 3 times/year from 2014 to 2016. Data collected included HLA specificities, MFI values, class I/class II cutoffs, vendor information, and lot numbers. The coefficient of variations (%CV) were calculated using the center-specific MFI values to analyze the variability in the reporting of antibody strength among labs. Results Participants tested 36 total samples over 9 Exchanges. Among labs, their positive cutoff values ranged broadly from 300 to 3000 for A, B, DR, and DQB1 loci and 300–15000 for C, DPB1, and DQA1 loci, as good agreement was achieved in detecting antibodies with MFI values >5000. However, in the reporting of antibody strength, there was variability. Table 1 lists the MFI %CV of class I/II loci for peak specificities reported with consensus. (No DQA specificities were included as none reached consensus.) Mean %CV ranged from 25% to 34% over the 9 Exchanges. Generally, in the presence of strong antibodies (MFI > 15000), %CV fell below 25%. As MFI strength decreased, the %CV increased, in some cases to above 60% when MFI values were Conclusions In conclusion, the data shows consistency in the detection of HLA antibodies among labs; however, variability in reporting positive cutoff values and antibody strength exists. Thus, educational activities should continue to provide standards for quality control of antibody testing methods. Download : Download high-res image (603KB) Download : Download full-size image