RESUMO
The high number of D variants can lead to the unnecessary use of Rh immune globulin, overuse of D- RBC units, and anti-D allommunization. D variant prevalence varies among ethnic groups, and knowledge of the main variants present in a specific population, their behavior in serologic tests, and their impact on clinical practice is crucial to define the best serologic tests for routine use. The present study aimed to explore the serologic profile of D variants and to determine which variants are most associated with false-negative D typing results and alloimmunization. Donor samples were selected in two study periods. During the first period, D typing was performed on a semi-automated instrument in microplates, and weak D tests were conducted in tube or gel tests. In the second period, D typing was carried out using an automated instrument with microplates, and weak D tests were performed in solid phase. Samples from patients typed as D+ with anti-D were also selected. All samples were characterized by molecular testing. A total of 37 RHD variants were identified. Discrepancies and atypical reactivity without anti-D formation were observed in 83.4 percent of the samples, discrepant D typing results between donations were seen in 12.3 percent, and D+ patients with anti-D comprised 4.3 percent. DAR1.2 was the most prevalent variant. Weak D type 38 was responsible for 75 percent of discrepant samples, followed by weak D type 11, predominantly detected by solid phase. Among the D variants related to alloimmunization, DIVa was the most prevalent, which was not recognized by serologic testing; the same was true for DIIIc. The results highlight the importance of selecting tests for donor screening capable of detecting weak D types 38 and 11, especially in populations where these variants are more prevalent. In pre-transfusion testing, it is crucial that D typing reagents demonstrate weak reactivity with DAR variants; having a serologic strategy to recognize DIVa and DIIIc is also valuable.
Assuntos
Doadores de Sangue , Sistema do Grupo Sanguíneo Rh-Hr , Humanos , Sistema do Grupo Sanguíneo Rh-Hr/imunologia , Sistema do Grupo Sanguíneo Rh-Hr/genética , Doadores de Sangue/estatística & dados numéricos , Reações Falso-Negativas , Tipagem e Reações Cruzadas Sanguíneas/métodos , Feminino , Isoanticorpos/sangue , Isoanticorpos/imunologia , Imunoglobulina rho(D)/imunologia , Imunoglobulina rho(D)/sangue , MasculinoRESUMO
BACKGROUND: The correct determination of D antigen could help to avoid alloimmunization in pregnant women and patients receiving blood transfusions. However, there are limitations in the identification of D variants as the partial and weak D phenotypes make the determination of D antigen a great challenge in the transfusion routine.' STUDY DESIGN AND METHODS: The molecular characterization of D variants was performed on blood donors from southeastern Brazil with atypical D typing. Furthermore, the serological profile of all RHD variant alleles identified was analyzed using different Anti-D clones. The prevalence of RHD alleles and genotypes found was compared with those described in other countries and in other regions from Brazil. RESULTS: Atypical serologic D typing occurred in 0.79 % of blood donors. The majority of RHD variant alleles (88 %) were first characterized by multiplex PCR and PCR-SSP as RHD*weak partial 4 (47 %), followed by RHD*weak D type 3 (29.9 %), RHD*weak D type 2 (3.9 %) and RHD*weak D type 1 (3.1 %). Genomic DNA sequencing characterized the RHD*weak partial 4 variants found in RHD*DAR1.2 (weak 4.2.2) (22 %), RHD*DAR3 (weak 4.0.1) (2.4 %), RHD*DAR3.1 (weak 4.0) (22 %) and RHD*DAR4 (weak 4.1) (0.8 %). RHD variant alleles associated with partial D, such as, RHD*DAU-4 (1.6 %), RHD*DAU-5 (2.4 %), RHD*DAU-6 (1.6 %), RHD* DIII type 8 (1.6 %), RHD*DVII (3.9 %) and RHD* DMH (0.8 %) were also observed. CONCLUSION: The prevalence of RHD variant alleles observed in this cohort differ from those found in other populations, including Brazilians from other regions. RHD allele distribution in specific regions should be considered for implementation of algorithms and genotyping strategies aiming at a more effective and safe transfusion.
Assuntos
Alelos , Doadores de Sangue , Polimorfismo Conformacional de Fita Simples , Sistema do Grupo Sanguíneo Rh-Hr/genética , Brasil , Feminino , Humanos , Masculino , Reação em Cadeia da Polimerase MultiplexRESUMO
BACKGROUND: Laboratory testing to identify the molecular basis of serologic weak D phenotypes is recommended to determine whether a pregnant woman or potential transfusion recipient should be managed as RhD-positive or RhD-negative. The variation in D antigen expression on RBCs, different potencies of anti-D typing reagents, lack of standardized test methods, and the subjectivity of interpreting agglutination reactions complicate the detection of D variants. We evaluated the correlation of agglutination scores by an automated immunoassay analyzer with D antigen densities determined by flow cytometry, and D variant types identified by molecular analysis. MATERIALS AND METHODS: We selected 273 blood donor samples with agglutination scores of less than 92 (4+), measured by an automated analyzer (NEO®, Immucor, Norcross, GA, USA). D antigen densities were measured by flow cytometry for 89 samples. Samples were classified as molecularly-determined weak D or partial D variants by multiplex PCR, PCR RFLP and DNA sequencing. RESULTS: All samples with a D antigen density ≥15% had an agglutination score >80 (4+). Agglutination scores for weak D types varied from 10 to 90. Agglutination scores for partial D antigens were graded with scores varying from 60 to 99. D antigen densities varied from 0.55% to 10.67% for weak Ds and 4.1% to 30.5% for partial Ds. DISCUSSION: Our results showed that score values follow a pattern among D variants that could be related to antigen density and to the RhD variant classification.
Assuntos
Tipagem e Reações Cruzadas Sanguíneas , Citometria de Fluxo , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Sistema do Grupo Sanguíneo Rh-Hr , Análise de Sequência de DNA , Aglutinação , Eritrócitos/metabolismo , Feminino , Humanos , Gravidez , Sistema do Grupo Sanguíneo Rh-Hr/sangue , Sistema do Grupo Sanguíneo Rh-Hr/genéticaRESUMO
The Rh blood group system is one of the most complex, polymorphic and immunogenic blood group systems in humans. Some individuals produce a weak or a partial D as a result of RHD and RHCE gene conversion events and RHD point mutations. Because the incidence of RHD variants differs considerably among ethnic groups, the objective of this study was to establish the frequency of blood donors carrying some weak and partial RHD, at the molecular level, in 400 blood donors from the North/Northwest of the state of Parana, Southern Brazil. Another 30 blood donors whose RhD typing results in serology were inconclusive were also included. In this mixed Brazilian population, the most frequent weak D types were 1, 4, 3 and 2 (frequencies of 4.35%, 2.32%, 1.46% and 0.29%, respectively; total of 8.41%) and partial D was found in 2.90% of samples carrying the RHD gene. For samples with inconclusive RhD typing, 53.33% of them presented weak and partial RHD, and 43.75% had concomitantly more than one RHD variant. Our results demonstrate the presence of Caucasian and African D variants. This knowledge can contribute to the safety of transfusion strategies in this ethnic admixture population.