A 13-Question Approach to Resolving Serological Discrepancies in the Transfusion Medicine Laboratory

Novel blood typing method by discrimination of hemagglutination and rouleaux using an erythrocyte aggregometer

BACKGROUND: In pretransfusion blood typing, pretreatments such as centrifugation and suspension of red blood cells (RBCs) and mixing them with sufficient amounts of reagents are required, but these steps are time-consuming and costly. OBJECTIVE: Aiming to develop a new blood typing method that requires no dilution and only a small amount of reagent, we attempted to determine blood type using syllectometry, an easy-to-use and rapid optical method for measuring the RBC aggregation that occurs when blood flow is abruptly stopped in a flow channel. METHODS: Samples of whole blood from 20 healthy participants were mixed with antibody reagents for blood typing at mixing ratios of 2.5% to 10% and measured with a syllectometry device. RESULTS: Amplitude (AMP), one of the aggregation parameters, showed significant differences between agglutination and non-agglutination samples at mixing ratios from 2.5% to 10%. Although there were significant individual differences in aggregation parameters, calculation of AMP relative to that of blood before reagent mixing reduced the individual differences and enabled determination of blood type in all participants. CONCLUSIONS: This new method enables blood typing with a small amount of reagent, without the time-consuming and labor-intensive pretreatments such as centrifugation and suspension of RBCs.

Portable paper-based device for ABO and RhD typing using smartphone interpretation: Optical answer sheet reading concept

The slide method for ABO blood group typing is commonly used for mobile blood donation and field applications because the test is easy, cost-effective, can be completed in a few minutes and requires a small volume of reagents. However, the reaction must be observed by an individual with expertise within 2 min; otherwise, drying of the reagent will give a false positive result. Moreover, the blood typing reagents must be stored at 4 °C. The present study aimed to create a paper-based device for ABO and RhD blood typing and combine an optical answer sheet reading concept to read and interpret the results with Android smartphones. The invention of this device involved the use of simple filter paper and conjugate pads that were treated with anti-A, -B and -D antibodies. Blood type can be visually identified from the detection zone at the end of the filter paper. An Android smart phone was designed to read the detection zone, interpret the data and subsequently report the results on the user's smartphone. A helpful color chart was also designed for blood typing interpretation by the naked eye. The use of smartphones can reduce human error in data reading and interpretation. In conclusion, ABO and RhD typing with paper-based devices using a smartphone interpretation may provide further advantages for home-based users, mobile blood donation sites and field applications.

A rapid, point-of-care red blood cell agglutination assay detecting antibodies against SARS-CoV-2

The COVID-19 pandemic has caused significant morbidity and mortality. There is an urgent need for serological tests to detect antibodies against SARS-CoV-2, which could be used to assess past infection, evaluate responses to vaccines in development, and determine individuals who may be protected from future infection. Current serological tests developed for SARS-CoV-2 rely on traditional technologies such as enzyme-linked immunosorbent assays (ELISA) and lateral flow assays, which have not scaled to meet the demand of hundreds of millions of antibody tests so far. Herein, we present an alternative method of antibody testing that depends on one protein reagent being added to patient serum/plasma or whole blood with direct, visual readout. Two novel fusion proteins, RBD-2E8 and B6-CH1-RBD, were designed to bind red blood cells (RBCs) via a single-chain variable fragment (scFv), thereby displaying the receptor-binding domain (RBD) of SARS-CoV-2 spike protein on the surface of RBCs. Mixing mammalian-derived RBD-2E8 and B6-CH1-RBD with convalescent COVID-19 patient serum and RBCs led to visible hemagglutination, indicating the presence of antibodies against SARS-CoV-2 RBD. B6-CH1-RBD made in bacteria was not as effective in inducing agglutination, indicating better recognition of RBD epitopes from mammalian cells. Given that our hemagglutination test uses methods routinely used in hospital clinical labs across the world for blood typing, we anticipate the test can be rapidly deployed at minimal cost. We anticipate our hemagglutination assay may find extensive use in low-resource settings for detecting SARS-CoV-2 antibodies.

A Flow Cytometric Study of Reagent Cells to Resolve ABO Typing Discrepancy

OBJECTIVES

RBC alloantibodies can lead to ABO grouping discrepancies unrelated to A or B antigens or antibodies posing challenges in the blood bank testing. Routine blood bank testing and flow cytometry were used to immunophenotype reagent cells and elucidate the cause of ABO discrepancies in two patients.

METHODS

ABO discrepancy was identified in two patients after transfusion with several units of RBCs. For both patients, the pretransfusion type and screen demonstrated blood group A. Eight and 16 days later, both patients showed an apparent antibody to reagent group A cells, which prompted additional study with patients' samples and flow cytometric testing of commercial reagent cells.

RESULTS

In both patients' specimens, posttransfusion evaluation demonstrated an emerging antibody to the Kell antigen (K). The RBCs of both patients typed negative for K, and both were transfused with K-positive RBCs. Flow cytometric analysis of reagent RBCs demonstrated that five of seven lot numbers were positive for K.

CONCLUSIONS

Emerging anti-K antibody led to agglutination of the K-positive reagent A1 cells, highlighting the importance of considering RBC alloantibodies and the composition of reagent cells when interpreting cases with an apparent ABO grouping discrepancy.

Anti-A and anti-A,B monoclonal antisera with high titers favor the detection of A weak phenotypes

OBJECTIVES

This study aimed to evaluate the reactivity and the titers of commercial anti-A and anti-A,B antisera in the detection of A weak antigen expression in human red blood cells.

BACKGROUND

Commercial monoclonal antisera for ABO phenotyping are useful reagents allowing the identification of the four main ABO phenotypes (A, B, AB, and O). However, the reactivity of these commercial reagents can not be evident when the A or B antigens are weakly expressed, and these antisera have low titers.

METHODS/MATERIALS

Six samples from blood donors and five samples from patients with ABO forward and reverse discrepant phenotyping were evaluated. The ABO phenotyping was carried out with different commercial monoclonal anti-A and anti-A,B antisera under different temperatures, using test tubes and gel column agglutination.

RESULTS

Monoclonal anti-A antisera with titers less than 256 and anti-A,B with titers less than 128 failed to detect the weak expression of A antigen in 73% and 67% of the A weak phenotypes, respectively. Titres equal to or higher than 2048 (anti-A) and 1024 (anti-A,B) showed better reactivity, independent of the cell clone.

CONCLUSION

Our data indicate that anti-A and anti-A,B antisera with high titers give better reactivity with red blood cells carrying A weak antigen expression.