HLA-DR AND DQ TYPING BY POLYMERASE CHAIN-REACTION USING SEQUENCE-SPECIFIC PRIMER MIXES REDUCES THE INCIDENCE OF PHENOTYPIC HOMOZYGOSITY (BLANKS) OVER SEROLOGY

Because of the inherent difficulties in allele assignment with HLA-DR serological typing, in 1993 our organ procurement organization-based H LA laboratory replaced serology with the molecular method of polymeras e chain reaction using sequence-specific primer mixes (PCR-SSP) to typ e for DR and DQ at a resolution level equivalent to that of serologica lly defined antigens. In this study, we compared the incidence of DR b lanks, where allocative homozygosity occurred, and graft outcome durin g our serology epoch (1987-1993) with that of our molecular epoch (199 3-1996), The incidence of DR blanks by PCR-SSP (17.0%; 138/1101) was s ignificantly lower (P<0.005) than in the serology epoch (21.5%; 569/26 47), Although DQ is not a component of the allocation algorithm, the i ncidence of blanks in the molecular era (21.9%; 196/895) was 46% lower (P<0.001) than in the serology epoch (40.8%; 931/2277). Graft surviva l in 163 cadaveric renal transplant recipients for whom molecular DR a llocation occurred (patient and donor were molecularly typed) showed t hat PCR-SSP typing had no significant effect on 2.5-year graft surviva l for patients mismatched for 0 (97%), 1 (90%), or 2 (94%) HLA-DR anti gens (P=0.4; log-rank), In conclusion, molecular typing lowered the ra te of DR and DQ blanks, but molecular matching for HLA DR and DQ did n ot influence graft outcome at 2.5 years.