Flexible automated platform for blood group genotyping on DNA microarrays.

The poor suitability of standard hemagglutination-based assay techniques for large-scale automated screening of red blood cell antigens severely limits the ability of blood banks to supply extensively phenotype-matched blood. With better understanding of the molecular basis of blood antigens, it is now possible to predict blood group phenotype by identifying single-nucleotide polymorphisms in genomic DNA. Development of DNA-typing assays for antigen screening in blood donation qualification laboratories promises to enable blood banks to provide optimally matched donations. We have designed an automated genotyping system using 96-well DNA microarrays for blood donation screening and a first panel of eight single-nucleotide polymorphisms to identify 16 alleles in four blood group systems (KEL, KIDD, DUFFY, and MNS). Our aim was to evaluate this system on 960 blood donor samples with known phenotype. Study data revealed a high concordance rate (99.92%; 95% CI, 99.77%-99.97%) between predicted and serologic phenotypes. These findings demonstrate that our assay using a simple protocol allows accurate, relatively low-cost phenotype prediction at the DNA level. This system could easily be configured with other blood group markers for identification of donors with rare blood types or blood units for IH panels or antigens from other systems.

Weak D phenotypes and transfusion safety: where do we stand in daily practice?

BACKGROUND: Weak D Types 1, 2, and 3 recipients cannot be immunized when exposed to D antigen. Molecular biology is very efficient to type weak D variants but rarely implemented in daily practice. The serologic typing practice of weak D in a Caucasian patient population was analyzed and a transfusion strategy is proposed. STUDY DESIGN AND METHODS: Samples typed either ddCcee or ddccEe in routine laboratories were tested with the indirect antiglobulin test (D(u) test). D(u)-positive samples were screened for weak D alleles Types 1, 2, and 3 and further tested with immunoglobulin M (IgM) anti-D reagents, used in a fully automated device. RESULTS: A total of 468 of 55,162 samples were found to be ddCcee or ddccEe. Ninety-three expressed weak D after the D(u) test leading to D+ assignment for transfusion. Seventy-three percent of D(u)-positive samples were weak D alleles Type 1, 2, or 3. Almost all weak D Types 1, 2, and 3 were positive with IgM reagents in gel matrix with an automated device. Other variants that could be potentially associated with anti-D alloimmunization, however, were also positive. CONCLUSION: Serology is very sensitive to detect weak D Types 1, 2, and 3, but there is no cutoff to distinguish variants of clinical significance. When molecular analysis is not available, it is proposed that a D+ status for blood recipients found to be weak D with a sensitive method be assigned, except for women of childbearing age or younger, because of the remaining possibility to be partial D or other rare weak D who can be immunized.