Identifying D-positive donors using a second automated testing platform

Because of the variability of D expression, one method may be inadequate to correctly classify donors with variant RHD alleles. We evaluated the use of a solid -phase automated platform (ImmucorGamma Galileo) to confirm D- test results obtained on first-time donors on the Beckman Coulter PK7300 automated microplate test system. Samples with discordant results were analyzed by serologic tube methods, RHD genotyping using the BLOODchip platform (Progenika) and, if necessary, sequencing. We estimated the number of cases of alloimmunization in women younger than 50 years likelyto be prevented by the addition of Galileo testing. From May 2011 to May 2012, 910,220 donor samples were tested; 15,441 were first-time donors with concordant D- results. Five donors tested D- on the PK7300 and weak D+ on the Galileo; one was found to be a false positive on further testing. On manual testing, the other four donors had positive indirect antiglobulin test results with one to three of the antisera used and were C+. On BLOODchip testing, two donors were classified as D+, and two were assigned a "no call". D variants included weak D type 67, weak D type 9, and two novel variants. Approximately 10 percent of D- units are transfused to women younger that 50 years. Assuming an alloimmunization rate of 30 percent, use of the Galileo would prevent approximately one alloimmunization every 5 to 6 years in this patient group. We conclude that the yield of preventing alloimmunization in this population by adding a second automated seologic testing platform is very low.