Impact of RHD genotyping on transfusion practice in Denmark and the United States and identification of novel RHD alleles.

BACKGROUND: Reduced D antigen on red blood cells (RBCs) may be due to "partial" D phenotypes associated with loss of epitope(s) and risk for alloimmunization or "weak" D phenotypes that do not lack major epitopes with absence of clinical complications. Genotyping of samples with weak and discrepant D typing is recommended to guide transfusion and RhIG prophylaxis. The goal was to compare the impact of RHD genotyping on transfusion practice in two centers serving different populations. STUDY DESIGN AND METHODS: Fifty-seven samples from Denmark and 353 from the United States with weak or discrepant D typing were genotyped. RBC typing was by multiple methods and reagents. DNA isolated from white blood cells was tested with RBC-Ready Gene D weak or CDE in Denmark or RHD BeadChip in the United States. RHD was sequenced for those unresolved. RESULTS: Of Caucasian samples from Denmark, 90% (n = 51) had weak D types 1, 2, or 3; two had other weak D, two partial D, and two new alleles. In diverse ethnic U.S. samples, 44% (n = 155) had weak D types 1, 2, or 3 and 56% (n = 198) had other alleles: uncommon weak D (n = 13), weak 4.0 (n = 62), partial D (n = 107), no RHD (n = 9), and new alleles (n = 7). CONCLUSION: Most samples with weak or variable D typing from Denmark had alleles without risk for anti-D. In U.S. samples, 48% could safely be treated as D+, 18% may require consideration if pregnancy possible, and 34% could potentially benefit from being treated as D-. Black and multiracial ethnicities were overrepresented relative to population.

Minimal variation in anti-A and -B titers among healthy volunteers over time: Implications for the use of out-of-group blood components.

BACKGROUND: Using potentially out-of-group blood components, like low titer A plasma and O whole blood, in the resuscitation of trauma patients is becoming increasingly popular. However, very little is known whether the donors' anti-A and/or anti-B titers change over time and whether repeated titer measurements on the same donor are required to ensure that each donation produces a low titer product. METHODS: The anti-A and/or anti-B titers were measured on 56 healthy adult volunteers (47 blood donors; nine blood center personnel) every 3 months for 12 consecutive months using an automated solid phase analyzer. The results were expressed as log2 titer steps (e.g., titer 32 = 5 titer steps). RESULTS: Minor variations in the average anti-A and/or anti-B titers were seen over time; the maximum individual SD in each group was 1.50 (IgG anti-A) or 1.00 (IgM anti-A, IgM, and IgG anti-B). When the SDs for the four titer measurements from all 56 volunteers were combined as appropriate, the highest overall combined SD was 0.47 titer steps for IgG anti-A. This value corresponds to a 95% confidence interval for intraindividual variation in this antibody's titer over 12 months of 0.96 titer steps. Thus, based on one measurement, an IgG anti-A with a titer step of, for example, 6 would be expected to be in the range of titer step 5 to titer step 7 over the course of 1 year with 95% probability. CONCLUSION: The titers of anti-A and/or anti-B among healthy adults are stable over at least 1 year. This suggests that repeated titer measurements within a year on the same donor are not necessary if donations are made at 3 months or longer intervals. LEVEL OF EVIDENCE: Diagnostic study, level V.