Predictive blood group genetics in hemolytic disease of the fetus and newborn: a 10‐year review of a laboratory evaluation of amniotic fluid‐derived DNA

Abstract

To identify the types of requests, the patterns of testing, and the error rates associated with the genetic identification of fetuses at risk for immune-mediated hemolytic disease. Retrospective review of the laboratory information system for all fetal blood group genotyping tests performed at Mount Sinai Hospital, Toronto, Canada from January 1997 to December 2006. Amniotic fluid-derived DNA, from 220 women (243 pregnancies), was tested for one or more antigens (279 tests) when the father was heterozygous for the inferred blood group antigen or was unavailable. The PCR amplification failure rate of amniotic fluid-derived DNA was 5.0%. When the father was considered hemizygous for RHD or was not available, the fetus was positive in 68.6% and 72.7% of cases, respectively. Two amniotic fluid-derived DNA KEL1 SSP-PCR results did not correlate with the result determined from cultured amniocyte DNA. Paternal RHD hemizygosity may be overestimated. Thus, we recommend that RHD zygosity be established by molecular analysis of the RHD breakpoint. Cultured amniocytes should be reserved for testing if the amniotic fluid-derived DNA is inconclusive due to PCR amplification failure. We use PCR-RFLP genotyping methods for RHCE*E/RHCE*e (Rh E/e), KEL1/KEL2 (K/k), FYA/FYB (Fy(a/b)), and JKA/JKB (Jk(a/b)).