Multiplex ligation-dependent probe amplification (MLPA) assay for blood group genotyping, copy number quantification, and analysis of RH variants.

The blood group multiplex ligation-dependent probe amplification (MLPA) is a comprehensive assay, developed for genotyping the majority of clinically relevant blood group antigens in both patients and donors. The MLPA is an easy method to apply and only requires a thermal cycler and capillary electrophoresis equipment. Because the molecular basis of blood group antigens can be a single nucleotide polymorphism, an insertion/deletion polymorphism, or genetic recombination, a single assay such as the MLPA to facilitate these different types of genetic variation is a prerequisite in blood group typing. An MLPA assay allows the simultaneous detection of up to 50 polymorphisms in a single tube. The blood group MLPA currently consists of three separate probe pools targeting 104 different blood group alleles of 18 blood group systems. The assay is performed in a 96-well plate; therefore, a maximum of 32 genomic DNA samples can be processed simultaneously. Results are available within 24 hours,and software for analysis of the MLPA results is available free of charge. In addition to the analysis of genetic variation in blood group genes, a major advantage of the test is the ability to detect aberrations in gene copy numbers, which is especially useful for the determination of homo- or hemizygous status of RHD or other blood group genes and for detection of blood chimerism. A relatively large number of RH wild-type and mutation-specific probes are included in the assay, allowing an extensive analysis of RHD variants. In our reference lab in the Netherlands, the MLPA was validated to detect RH variants in patients, donors, and pregnant women. Furthermore, we have used the MLPA to provide comprehensive typing after blood transfusion of 52 blood group antigens simultaneously, in patients with red cell autoantibodies or patients with rare phenotypes.