Impact of a confirmatory RhD test on the correct serologic typing of blood donors

Abstract

BackgroundThe RHD gene is highly polymorphic, which results in a large number of RhD variant phenotypes. Discrepancies in RhD typing are still a problem in blood banks and increase the risk of alloimmunization. In this study, the RhD typing strategy at a blood bank in Brazil was evaluated.MethodsOne-hundred and fifty-two samples typed as RhD negative and C or E positive by routine tests (automated system and indirect antiglobulin test using the tube technique) were reevaluated for RhD status by three methods. The method with the best performance was implemented and evaluated for a period of one year (n = 4897 samples). Samples that were D positive exclusively in the confirmatory test were submitted to molecular analysis.ResultsThe gel test for indirect antiglobulin testing with anti-D immunoglobulin G (clone ESD1) presented the best results. Seventy samples (1.43%) previously typed as RhD negative showed reactivity in the gel test for indirect antiglobulin testing and were reclassified as D positive. D variants that may cause alloimmunization, such as weak D type 2 and partial DVI, were detected.ConclusionThe confirmatory RhD test using the gel test for indirect antiglobulin testing represents a breakthrough in transfusion safety in this blood center. Our results emphasize the importance of assessing the blood group typing strategy in blood banks.

Performance evaluation study of ID RHD XT, a new genotyping assay for the detection of high‐prevalence RhD negative and weak D types

“…When the number of genotyped weak D type 1, 2 or 3 types is calculated over all genotyped weak D, frequencies range from 87% in Croatia to 100% in Albania . Several reasons can be invoked to explain such discrepancies: (1) anti‐D serology tests used traditionally for donors in the blood banks, resulting in weak D type 1, 2 or 3 samples being mistyped as positive for the first‐level screening (therefore, no second‐level confirmation is performed); (2) different monoclonal anti‐D are used among different studies; (3) some studies calculate frequency percentages using the serological weak D samples as total number of samples, while others use the genotyped weak D samples as total number of samples; (4) studies have different sample sizes and origins; (5) inclusion of samples because of anti‐D production ; and (6) DEL samples .…”

How do we approach dilemmas in red cell testing?

“…Donors who are identified as D− on both anti‐D reagents are subjected to weak D testing utilizing the antihuman globulin phase. Donors should be labelled as D− only if the weak D test is negative .…”

Impact on patient of the detection of weakly expressed RhD antigens in blood donors

“…It is consensus that molecular techniques allowed the start of a new stage of blood donor typing, including several strategies to identify RhD variants that are potentially immunogenic in apparently RhD-negative donors, as shown in several studies. 11 , 12 , 13 , 14 , 15 , 16 , 17 Furthermore, in some of these studies, these variants were also found to be associated with the C and E antigens of the Rh system, 11 , 12 , 14 , 15 although some RhD subtypes were found in ccee individuals. 13 Techniques have now identified more than 200 variants of the D antigen, including weak D, D partial and DEL types.…”

“…A study by Schmidt et al 14 showed positive results for the RhD antigen in 5.9% of 152 blood donors – who had been previously identified as RhD negative in routine examinations – when using anti-D IgG monoclonal antibodies (clones ESD1, MS-26 and TH-28) in gel cards. In the same study, the authors evaluated another population of 4897 donors from different regions of Minas Gerais state, Brazil, who had all been previously phenotyped as D negative in the indirect antiglobulin test (IAT), with clones MS-26 and TH-28, and 70 (1.43%) individuals showed weak reactivity with ESD1 anti-D antibodies.…”