Identification of allelic variants discovered by atypical typing results on the NEO/Echo platforms.

Some individuals are at risk of anti-D alloimmunization if they inherit D antigens that are qualitatively and/or quantitatively different than wild-type D. We hypothesized that patients who showed serologically inconsistent, weak, or historically discordant D typing results by microplate direct agglutination (MDA) on NEO or Echo (Immucor, Norcross, GA) might be at risk of carrying allelic variants. The present study was designed to evaluate patients with allelic variants if they presented with weakly reactive D typing results on the NEO or Echo. Patients were selected for genotyping if their specimens showed weak reactivity with either series 4 or series 5 anti-D typing reagent, if the strength of reactivity was ≤1+ on the NEO or Echo, or if historical or current D typing results were discordant with current results. Patients selected for genotyping were also tested by saline tube testing using the same anti-D series 4 and 5 reagents. Genotyping was performed by the Immucor genotyping laboratory in Warren, NJ. Of 80 patients whose samples met study inclusion, 52 (65.0%) were found to have allelic variants. Sixteen patients (20.0%) expressed possible Ceppellini effect reactivity. Most importantly, 51.25 percent of the patients who presented with weakly reactive D typing results by MDA testing on the NEO (≤1+) or Echo (≤1+) had allelic variants that were associated with the potential for anti-D alloimmunization. Laboratories that use MDA testing on the Neo or Echo for D typing should consider that female patients of childbearing age might be at risk of anti-D alloimmunization if they are classified as D+ based on weakly reactive D typing results. Some individuals are at risk of anti-D alloimmunization if they inherit D antigens that are qualitatively and/or quantitatively different than wild-type D. We hypothesized that patients who showed serologically inconsistent, weak, or historically discordant D typing results by microplate direct agglutination (MDA) on NEO or Echo (Immucor, Norcross, GA) might be at risk of carrying allelic variants. The present study was designed to evaluate patients with allelic variants if they presented with weakly reactive D typing results on the NEO or Echo. Patients were selected for genotyping if their specimens showed weak reactivity with either series 4 or series 5 anti-D typing reagent, if the strength of reactivity was ≤1+ on the NEO or Echo, or if historical or current D typing results were discordant with current results. Patients selected for genotyping were also tested by saline tube testing using the same anti-D series 4 and 5 reagents. Genotyping was performed by the Immucor genotyping laboratory in Warren, NJ. Of 80 patients whose samples met study inclusion, 52 (65.0%) were found to have allelic variants. Sixteen patients (20.0%) expressed possible Ceppellini effect reactivity. Most importantly, 51.25 percent of the patients who presented with weakly reactive D typing results by MDA testing on the NEO (≤1+) or Echo (≤1+) had allelic variants that were associated with the potential for anti-D alloimmunization. Laboratories that use MDA testing on the Neo or Echo for D typing should consider that female patients of childbearing age might be at risk of anti-D alloimmunization if they are classified as D+ based on weakly reactive D typing results.