UTILITY OF LABSCREEN FOR THE IDENTIFICATION AND CHARACTERIZATION OF HLA ALLOANTIBODIES

7.2
TITLE: UTILITY OF LABSCREEN FOR THE IDENTIFICATION AND CHARACTERIZATION OF HLA ALLOANTIBODIES

Robert A. Bray, Lisa Wilmoth–Hosey, Pam Chapman, Howard M. Gebel.

Pathology, Emory University Hosptial, Atlanta, GA

HLA antigen–specific microparticle assays have advanced our understanding of the humoral immune response to alloantigens. Presently, two microparticle platforms for antibody detection: are available; standard flow cytometry and Luminex. In this study we compared One Lambda`s Luminex–based microparticle LabScreen assay to their Flow Specific Bead assay. We compared the concordance of 110 sera for the presence or absence of class I/II antibodies, PRA percentage and complete specificity, to the results obtained with the Luminex platform. Sample distribution was as follows: 22 samples (20%) were Class I +/Class II –; 22 samples (20%) were Class I –/Class II +; 50 samples (45%) were Class I +/Class II +; and 16 samples (15%) were negative for both Class I and Class II antibody. Testing was performed in 96–well microtiter plates, using the “spin and flick” technique with 50ul of serum. Flow Specific Beads were interpreted by visual inspection of histograms while LabScreen results were interpreted using “in–house” software and normalization algorithm. Initial evaluation showed 97% concordance for the presence or absence of antibody. Three discordant samples, two LabScreen(+) and Flow Specific Bead(–) and one Flow Bead(+) but LabScreen (–), were shown to each contain antibodies that reacted to the respective plastic particles and were not HLA antibodies. The r–values for PRA and specificity were 0.93 and 0.88 (Class I) and 0.94 and 0.94 (Class II), respectively. No trend for PRA levels was observed, but specificity was more easily assigned by LabScreen. This difference was due to the reporting of LabScreen results in quantitative fluorescence values.

In summary, the LabScreen demonstrated similar sensitivity but increased specificity compared to the Flow Specific Beads. The ability to quantify fluorescence significantly assisted with specificity analysis. In conclusion, the LabScreen assay is an alternative to Flow Specific Beads for both PRA and Specificity analysis. In fact, since both HLA antibody screening and HLA typing can be performed on this single platform, the Luminex–based assays may be a most desirable single methodology for the HLA laboratory.