Testing controls demonstrates a high prevalence of non-HLA antibody positivity using pre-defined cutoff threshold in...

Measuring non-HLA antibodies is a potentially important tool in assessing allograft dysfunction and needs to be correlated with clinical outcomes. Thus, determining the antibody distribution in healthy populations is important before correlating with clinical events. Using male blood donors, we selected a low immunological risk control cohort.

We analyzed samples from 92 male, non-transfused blood donors (donors) to assess the detection of antibodies in a normal population cohort using a non-HLA 33 antigen multiplex commercial assay.

At manufacturer's suggested cutoff threshold (COT) of 75 % percentile, no donors had negative results and at 95 % percentile only three donors were negative across all 33 antigens. At each of the manufacturer's COT, the median (IQR) number positive antibody bead tests per donor was 13 (10-17), 11 (8-13) and 7 (5-10) at 75th, 85th and 95th percentile COT, respectively. There was poor correlation between manufacturer's COT and locally generated COT (range r = 0.520 to 0.595). The percentage of donors who had three or more positive antibody bead tests was: 98.9 % at 75th COT; 95.7 % at 85th COT and 93.5 % at 95th COT.

Considering the high proportion of positive results in a low immunological risk cohort, application of non-HLA antibody measurement in a diseased cohort is not optimal, and difficult to correlate with clinical events. Further studies to determine normal detection rates are needed for assay COT and clinical application in diseases.