Molecular Diagnostics in Transfusion Medicine: MALDI-TOF MS for Blood Bankers- The Alternative Approach for Genotyping

Serology, defined as antibody-based diagnostics, has been held as the analytical gold standard in transfusion medicine. However, at the present time, the influence of molecular diagnostics in transfusion medicine is rapidly growing. These methods can improve tissue typing (HLA typing), increase safety of blood products (NAT testing of infectious diseases), and enable blood group typing in difficult circumstances (prenatal non-invasive RhD typing and/or post-transfusion of blood products). Generally speaking, molecular testing involves determining the presence of single nucleotide polymorphisms (SNPs). Blood group antigens mostly result from single nucleotide differences in critical positions. However, most blood group systems cannot be determined by looking at a single SNP. To identify members of a blood group system, a number of critical SNPs have to be considered. Current platforms used to perform molecular diagnostics are predominantly gel-based, involving time-consuming multiple manual steps. To employ molecular methods in transfusion medicine in the future, the development of higher-throughput SNP genotyping, non-gel based platforms that allow rapid, costeffective screening are essential. Because of its potential for automation, high throughput and cost effectiveness, the special focus of this review is a relatively new technique: blood group genotyping by MALDI-TOF MS. Although matrix-assisted laser desorption/ionisation, time-of-flight mass spectrometry (MALDI-TOF MS) has been previously reported for high throughput blood group genotyping, those reports are limited to only a few blood group systems. This report is timely as promising preliminary results have recently been published from a large cooperative Swiss-German project that aimed to employ MALDI-TOF MS for the molecular detection of the blood groups Rh, Kell, Kidd, Duffy, MNSs, a comprehensive collection of low incidence antigens, as well as the platelet and granulocyte antigens HPA and HNA, representing a total of 101 blood group antigens, encoded by 170 alleles, respectively. From this report, the observed success rates, data quality and concordance with known blood group types are highly impressive, underlining the accuracy and reliability of this cost-efficient high throughput method. Furthermore, Kell and RhD genotyping have been performed on foetal DNA from maternal plasma with excellent results. Additionally, current reports describe MALDI-TOF MS as a technology with short time-to-resolution, ability for high throughput, and cost efficiency when used in genetic analysis, clinical chemistry, microbiology, pharmaco-genetics, oncology and haematology. In summary, this paper examines a new technological approach for high throughput blood group genotyping by means of MALDI-TOF MS.