Increased but stable isoagglutinin titers in hemodialysis patients

Practice of ABO antibody titration in a transplant center: From tube method to manual gel column testing to automated column agglutination technology

BACKGROUND AND OBJECTIVES

High-quality ABO antibody titre testing is required for ABO-incompatible haematopoietic stem cell transplantation and kidney transplantation. To assess the feasibility of automated ABO titration as an alternative to manual and semi-automatic titration during the peri-transplant period, a comparative study was conducted internally in a transfusion medicine laboratory.

MATERIALS AND METHODS

This study was performed in two stages. Firstly, the differences in anti-A/B detecting using conventional tube test (CTT) and manual column agglutination technology (CAT) were compared in group O pregnant women. Then, manual and automated CAT were applied to simultaneously detect ABO antibody levels in non-AB-group adult haematological oncology patients.

RESULTS

In the first stage, four groups of 192 comparable results were generated from 48 subjects, which showed a high correlation between CTT and manual CAT (p < 0.001). However, the detection sensitivity of the latter was at least 1 fold higher dilution than that of the former. Fifty-six patients were tested in the second stage by simultaneous manual and automated CAT, and the paired titers differed within an acceptable range (±1 fold dilution). However, the concordance was slightly higher in group IgM (85.4%) than in group IgG (80.5%). Blood group specificity of ABO titers was also observed in this population, and no association between titers and other factors was found.

CONCLUSION

Automated CAT standardises ABO titre testing and saves labor costs, although manual review of weak positive reactions is still necessary. Due to the blood group specificity of ABO antibodies, special attention should be paid to the quality control and clinical relevance of titre testing for group O recipients in ABO-mismatched transplantation.

Quantification of anti-A of IgM or IgG isotype using three different methodologies

BACKGROUND

Reliability of ABO-antibody measurement is important in the context of supplying low-titer ABO incompatible plasma-containing blood products. This study investigated the correlation of anti-A measurements between three different titer methodologies.

METHODS

Thirty-four blood group O individuals were included. IgM and IgG anti-A was measured by three different methods: (1) manual method (Bio-Rad ID-gel card), (2) automated method (Immucor NEO), (3) flow cytometry (FC) with calibration in molecules of equivalent fluorochrome (MEF). Data were log2 transformed to titer steps (TS) and log2 MEF, respectively. All three methods were benchmarked against the 14/300 WHO anti-A/anti-B standard reagent.

RESULTS

The correlation between the manual and automated methods was statistically significant for both IgM (Spearman's r_s  = 0.89, p < .0001) and IgG (r_s  = 0.95, p < .0001). The mean TS difference between the manual and automated methods was 0.61 for IgM (p = .0033) and 2.1 for IgG (p < .0001). The manual method yielded IgM titer results that were generally 1 titer step higher than the automated method, whereas for the IgG titrations the difference was generally a median of 2 TS higher. The FC median log2 MEF level was significantly correlated with TS of IgG and IgM for both manual and automated agglutination-based titer methods (0.69 ≤ r²  ≤ 0.91). With the WHO standard reagent, the manual method produced the expected results while the automated method's results were 1 TS lower for both IgM and IgG at all dilutions tested.

CONCLUSION

These results indicate that all three methods are suitable for measuring anti-A in group O whole blood.

Challenges in antibody titration for ABO-incompatible renal transplantation

BACKGROUND AND OBJECTIVES

Accurate and regular monitoring of anti-A and anti-B titres pre- and post-transplantation plays a crucial role in the clinical management of patients receiving ABO-incompatible renal transplants. There is no standardized protocol or an external quality assurance program (EQA) currently available for this testing in Australia. The aim of this study was to investigate the diversity of techniques, test platforms and reagents that were currently in use in various laboratories with the aim of developing an EQA.

MATERIALS AND METHODS

An online survey was sent to the participants enrolled with the Royal College of Pathologists of Australasia Quality Assurance Program (RCPAQAP) to assess their interest in participation in the pilot study. A total of 24 participants who expressed interest were sent the group O plasma, A₁ , A₂ and B cells to perform ABO titration using their own methods.

RESULTS

Participants reported a wide range of titre results, from 8 to 1024 for the anti-A titre using A₁ cells, from 2 to 128 for anti-A titre using A₂ cells and from neat to 32 for anti-B titre using B cells.

CONCLUSION

There was a wide variation in titre results between and within different technologies. These findings demonstrate the need for an ABO titration EQA. Development of a standard technique and participation in an EQA program should, over time, reduce variation and enable transferrable results across testing centres, which will assist in consistent clinical interpretation and better outcomes for patients.

Isohemagglutinin titering performed on an automated solid-phase and hemagglutinin-based analyzer is comparable to results obtained by manual gel testing

BACKGROUND

Isohemagglutinins (anti-A and anti-B) mediate hemolytic transfusion reactions, antibody-mediated rejection of solid-organ transplants, and delayed engraftment after stem cell transplant. However, quantification of isohemagglutinins is often labor intensive and operator dependent, limiting availability and interfacility comparisons. We evaluated an automated, solid-phase and agglutination-based antibody titer platform versus manual gel testing.

STUDY DESIGN AND METHODS

Plasma samples were obtained from 54 randomly selected patients. Titers were determined by our laboratory's standard assay (manual dilution followed by manual gel testing) and were compared to results obtained on a fully automated blood bank analyzer (Galileo NEO, Immucor). The analyzer determined immunoglobulin G (IgG) antibodies using solid-phase and immunoglobulin M (IgM) antibodies by direct hemagglutination.

RESULTS

Isohemagglutinin titers obtained by manual gel versus the automated assay generally (>80%) agreed within one doubling dilution, and always (100%) agreed within two dilutions. Among O samples, the gel titer and the highest titer obtained with the automated assay (either IgG or IgM) were similar in paired, nonparametric analysis (p = 0.06 for anti-A; p = 0.13 for anti-B). Gel titers from group A and group B patients were slightly higher than the highest titer obtained using the automated assay (p = 0.04 for group A; p = 0.009 for group B), although these differences were within the accepted error of measurement.

CONCLUSION

Manual and automated methodologies yielded similar isohemagglutinin titers. Separate quantification of IgM and IgG isohemagglutinins via automated titration may yield additional insight into hemolysis, graft survival after ABO-incompatible transplantation, and red blood cell engraftment after ABO-incompatible stem cell transplant.