Aim: Currently there are two commercially available Luminex assays for the detection of antibodies (Abs) directed against non-HLA antigens. These assays have different panels of antigens (Ags) but 25 of them are present on both. The aim of our study was to compare the reactivities against these 25 common Ags using the same sample cohort.
Method: Sera from 29 potential living kidney donors were run on two different Luminex non-HLA beads assays (Immucor/Werfen (IC) and One Lambda (OL)). Vendor suggested cutoffs were used for the analysis. All the analysis is restricted to the 25 common Ags.
Results: First we compared the strength of the reactivity that each serum had with each of the assays. For this, we calculated the Mean MFI values for each serum per assay using only the MFIs from the 25 common beads. The results (Fig 1) showed a poor correlation (0.309) between sera’s Mean MFIs. Then we compared if the beads carrying the same Ags were behaving similarly in both assays. Again, we calculated the Mean MFI value per Ags with the 29 sera. We found only a 0.667 correlation between the two assays. Next, we used IC’s and OL’s (95%) suggested positive cut off values to identify positive reactions. Fig 3 shows the number of positive beads per serum was different depending on the assay used (correlation is 0.427). Fig 4 also shows how the same Ag had a different number of sera reacting positive depending on the assay used (correlation -0.083). Importantly, each serum had a different pattern of reacting beads (Abs identified), and each bead had a different set of reacting sera depending on the assay used. There were 133 positive reactions with the OL assay and 135 with the IC assay, for a total of 268 positive reactions, but only 39 (14.5%) reactions were shared by both assays (not shown).
Conclusion: There was a low correlation in terms of strength of reactivity (MFI) and pattern of positive reactions for both sera and beads between the two assays. It is concerning that the non-HLA Abs identified for each serum is assay dependent. More work is needed to validate the use of these assays in the clinical laboratory.
