Optimizing pretransfusion antibody detection and identification: a parallel, blinded comparison of tube PEG, solid-phase, and automated methods

The impact of an antibody investigation algorithm emphasizing specificity on reducing potential false-positive warm autoantibody detection at a Canadian tertiary care centre

BACKGROUND AND OBJECTIVES

To reduce potential false-positive warm autoantibody (WAA) by solid-phase red cell adherence assay (SPRCA), our centre implemented a new antibody investigation algorithm (AIA) by classifying cases with panreactive SPRCA but negative saline-indirect antiglobulin test as 'antibody of undetermined significance' (AUS) after excluding clinically significant antibodies. We assessed the effects of the new AIA and subsequent alloantibody formation in patients with AUS.

MATERIALS AND METHODS

Samples from patients with positive SPRCA screens between 1 September 2017 and 31 August 2021 were selected for the study. Frequencies of antibodies classified by the old and new AIAs were compared using Fisher's exact test. Patient demographics, transfusion history and antibody formation in cases of AUS were collected.

RESULTS

A significant reduction in potential WAA frequencies from 127/1167 (11%) to 53/854 (6%) was observed (p < 0.001) when compared between the old and new AIAs among 2021 positive SPRCA antibody screens. While no patients with AUS later transitioned to potential WAA using the new AIA, four patients developed alloantibodies, including anti-E, anti-C, both anti-C and anti-E, and anti-Wra .

CONCLUSION

A significant reduction in the frequencies of potential false-positive WAA detection at our centre was observed after implementing the new AIA, leading to less resource and phenotypically matched red blood cell (RBC) use. Some patients still developed subsequent RBC alloimmunization, so clinically relevant alloantibodies should be carefully excluded before determining AUS, taking forming or evanescent antibodies into consideration.

A comparison of three column agglutination tests for red blood cell alloantibody identification

Objective

Commercial kits of column tests for pre-transfusion testing have progressively replaced conventional tube tests in most laboratories. Aim of this study was to compare three commercial test cell panels for the identification of irregular red blood cell (RBC) alloantibodies. Overall, 44 samples with a positive indirect antiglobulin test (IAT) by routine testing were used for comparison of following panels: Ortho RESOLVE^® panelC (Ortho Clinical Diagnostics (OCD), Milan, Italy), ID-DiaPanel(-P) (Bio-Rad Laboratories, CA, USA) and Identisera Diana(P) (Grifols, Barcelona, Spain). Column agglutination techniques were used, with microtubes containing either microgel (Bio-Rad/Grifols) or glass bead microparticles (Ortho).

Results

Alloantibody identification was possible in 38 samples, of which identical identification was shown in 33 samples by all methods. The remaining samples showed differences between certain methods, with the gel card system being superior to the glass card system for analyzing stored samples Considering that not all samples were evaluated in all three methods, the concordance rate reached 100% between Bio-Rad and Grifols, 90.5% between Bio-Rad and OCD, 86.5% between OCD and Grifols and 90.5% between all methods. Although differences in sensitivities were seen for specific antibodies, the three methods showed comparable performance for the identification of RBC alloantibodies.

A comparison of two automated methods for the detection and identification of red blood cell alloantibodies

BACKGROUND

The aim of this study was to compare the routine use of two automated systems (OrthoAutoVue Innova, microcolumn, and Immucor Galileo, solid phase) for the screening and identification of irregular red blood cell alloantibodies in samples, analysed in our Transfusion Service during 6 months of normal activity. The study focused particularly on an evaluation of the repeatability of the screening tests, the identification of antibody specificities and the identification of antibodies in samples showing discordant results.

MATERIALS AND METHODS

Overall 2,229 samples from potential blood donors (A), multiply transfused patients with blood disorders (DH), potential transfusion recipients (TS), and external cases (E) were studied. The protocols were carried out according to the manufacturers recommendations.

RESULTS

The screening tests detected 78 samples that were positive with both systems, while 18 were positive only with Immucor and 11 only with Ortho (thus, overall, Immucor detected 96 positive samples and Ortho 89 positive samples). The use of the respective identification panels enabled us to identify the antibodies in 65 samples with Immucor and in 61 samples with the Ortho system; 74 antibodies were identified with Immucor (55 with a single specificity and 19 with mixed specificities) and 68 antibodies with Ortho (51 and 17, respectively). In the remaining cases (31 samples for Immucor and 28 for Ortho), the antibody specificity was not identified. The two systems were found to be essentially similar. The Immucor system revealed a greater number of antibodies, mainly because of its greater sensitivity at detecting anti-D antibodies.

CONCLUSIONS

Both systems showed a repeatability of over 85%, demonstrating that automation of immunohaematological tests is advantageous. The specificity of the antibody was identified in 68% of the samples. Furthermore, using the two systems led to the identification of ten new antibodies (6 anti-D, 2 anti-E, 1 anti Le(a), and 1 anti-Vel), which would not have been detected had only one of the two methods been used.

Comparative sensitivity of solid phase versus PEG enhancement assays for detection and identification of RBC antibodies

Blood banks require a sensitive, specific, and efficient method to detect clinically significant RBC antibodies. Solid phase antibody screening methods are popular due to high sensitivity and automation. However, the high degree of reactivity detects "false positive" antibodies of questionable clinical significance leading to additional testing. We studied positive rates of Capture-R vs. PEG methods and categorized RBC antibodies identified by initial test results of 33,564 consecutive samples by Capture-R method. Capture-R was positive in 1,084/33,564 (3.2%) of samples. Using PEG as our "gold standard", PEG confirmed true positivity (i.e., > or = 1 cell reacting) in 710 Capture-R positive samples (65.5%); 374 Capture-R positive samples (34.5%) did not react in PEG (i.e., false positives). Of the 710 samples with true positivity, only 510 showed clinically significant alloantibodies. Using PEG as our "gold standard", only 2/3 of reactions by Capture-R were considered true positives. Because of ease and automation, Capture-R is popular as a screening test, but a more specific method may be helpful in order to identify truly significant alloantibodies.

Pretransfusion compatibility testing for red blood cell administration

The purpose of pretransfusion compatibility testing is to prevent incompatible red blood cell transfusions that could lead to immune mediated hemolytic transfusion reactions. Some hemolytic transfusion reactions may have serious sequelae including hemoglobinemia, disseminated intravascular coagulation, renal failure, and death. This article reviews the most comprehensive recent analyses of the laboratory methods used during pretransfusion compatibility testing in the United States. Most of the laboratory practice data have been published in the College of American Pathologists Transfusion Medicine Survey Sets and in a national survey called the Pre-Transfusion Testing Survey. This article couples and trends the data of these comprehensive surveys with an assessment of the literature to present the current practice of pretransfusion compatibility testing.