Will Genotyping Replace Serology in Future Routine Blood Grouping? - Opinion 5

Evaluation of molecular typing and serological methods in solving discrepant results of weak and partial D (Rh) in South Egypt

INTRODUCTION

Rh discrepancies produced by partial and weak D phenotypes are a problem during routine testing. Some blood units with weak and partial D expression may be missed by serology. Overcoming the limitations of serology can be achieved by molecular typing. Our objective was to evaluate currently used serologic methods with the molecular analysis in solving discrepant results of weak and partial D (Rh) in South Egypt.

PATIENTS AND METHODS

Fifty blood donor and patient samples with undetermined D phenotype were subjected to serology to define their phenotype using identification (ID)-Card "ID-partial RhD typing set" using six monoclonal anti-D panels, followed by molecular typing using polymerase chain reaction sequence-specific primer kit.

RESULTS

Molecular typing confirmed most of the serology results; two samples previously resolved as partial D Type 3 and DFR by serological methods were clarified by molecular techniques - one sample as weak Type 4 and the other sample as weak Type 3. Among the weak D alleles found in our study, Type 4 was the most common, with a frequency of 20%, followed by Type 3 (14%), Type 1 (8%), Type 2 (6%), and finally, Type 5 with a frequency of 3%. The most common types of partial D were partial D Type D5 (14%) and Type D3 (10%).

CONCLUSION

Our study identified D variants (weak D and partial D categories) of the antigen D and determined the frequency and composition of partial D and weak D alleles in our population. Molecular typing also confirmed most of the results obtained from serological methods.

BOOGIE: Predicting Blood Groups from High Throughput Sequencing Data

Over the last decade, we have witnessed an incredible growth in the amount of available genotype data due to high throughput sequencing (HTS) techniques. This information may be used to predict phenotypes of medical relevance, and pave the way towards personalized medicine. Blood phenotypes (e.g. ABO and Rh) are a purely genetic trait that has been extensively studied for decades, with currently over thirty known blood groups. Given the public availability of blood group data, it is of interest to predict these phenotypes from HTS data which may translate into more accurate blood typing in clinical practice. Here we propose BOOGIE, a fast predictor for the inference of blood groups from single nucleotide variant (SNV) databases. We focus on the prediction of thirty blood groups ranging from the well known ABO and Rh, to the less studied Junior or Diego. BOOGIE correctly predicted the blood group with 94% accuracy for the Personal Genome Project whole genome profiles where good quality SNV annotation was available. Additionally, our tool produces a high quality haplotype phase, which is of interest in the context of ethnicity-specific polymorphisms or traits. The versatility and simplicity of the analysis make it easily interpretable and allow easy extension of the protocol towards other phenotypes. BOOGIE can be downloaded from URL http://protein.bio.unipd.it/download/.

Extended blood group molecular typing and next-generation sequencing

Several high-throughput multiplex blood group molecular typing platforms have been developed to predict blood group antigen phenotypes. These molecular systems support extended donor/patient matching by detecting commonly encountered blood group polymorphisms as well as rare alleles that determine the expression of blood group antigens. Extended molecular typing of a large number of blood donors by high-throughput platforms can increase the likelihood of identifying donor red blood cells that match those of recipients. This is especially important in the management of multiply-transfused patients who may have developed several alloantibodies. Nevertheless, current molecular techniques have limitations. For example, they detect only predefined genetic variants. In contrast, target enrichment next-generation sequencing (NGS) is an emerging technology that provides comprehensive sequence information, focusing on specified genomic regions. Target enrichment NGS is able to assess genetic variations that cannot be achieved by traditional Sanger sequencing or other genotyping platforms. Target enrichment NGS has been used to detect both known and de novo genetic polymorphisms, including single-nucleotide polymorphisms, indels (insertions/deletions), and structural variations. This review discusses the methodology, advantages, and limitations of the current blood group genotyping techniques and describes various target enrichment NGS approaches that can be used to develop an extended blood group genotyping assay system.

Prospects for the provision of genotyped blood for transfusion

Blood group genotyping is gaining widespread adoption in blood centres and transfusion services. The current interest for a blood centre is its use as a screening tool to accurately predict donor phenotypes. However, not only is blood group genotyping used to screen for uncommon and rare types on a mass-scale, it can be used to optimize the inventory of multiple antigen-negative screened units. In addition, blood group genotyping provides blood types when antisera are not available, it can predict weak and variant antigens, and can aid in the resolution of ABO discrepancies. There are quality improvement benefits in blood group genotyping because it can screen for RHD alleles in Rh-negative blood donors and can be used to confirm that donors are suitable for reagent red cell production. It is possible that blood group genotyping information may be used as a donor recruitment tool. Given that genotyping can convey much more information about the expression of some complex antigens, e.g. hrB, Uvar, and Duffy, clinical trials are probably needed to show that genotyped or 'dry matched' transfusions are superior to phenotyped blood.