RESUMO

BACKGROUND: We evaluated different technological approaches and anti-D clones to propose the most appropriate serologic strategy in detecting the largest numbers of D variants in blood donors. METHODS: We selected 101 samples from Brazilian blood donors with different expressions of D in our donor routine. The tests were performed in immediate spin (IS) with eleven commercially available anti-D reagents in a tube and microplate. The D confirmatory tests for the presence of weak D included the indirect antiglobulin test (IAT) in a tube, gel and solid-phase red blood cell adherence (SPRCA). All DNA samples were extracted from peripheral blood and the D variants were classified using different molecular assays. RESULTS: The RHD variants identified by molecular analysis included weak D types (1, 2, 3, 11 and 38) and partial Ds (DAR1.2, DAR1, DAR3.1, DAU0, DAU2, DAU4, DAU5, DAU6, DMH and DVII). The monoclonal-monoclonal blend RUM-1/MS26 was the best anti-D reagent used in detecting the D antigen in the IS phase in a tube, reacting with 83.2% of the D variants, while the anti-D blend D175 + 415 was the best monoclonal antibody (MoAb) used in a microplate to minimize the need for an IAT, reacting with 83.2% of the D variants. The D confirmatory tests using SPRCA showed a reactivity (3 - 4+) with 100% of the D variant samples tested. CONCLUSION: Our results show that, even using sensitive methods and MoAbs to ensure the accurate assignment of the D antigen, at least 17% of our donor samples need a confirmatory D test in order to avoid alloimmunization in D-negative patients.

RESUMO

BACKGROUND: As a consequence of the homology and opposite orientation of RHD and RHCE, numerous gene rearrangements have occurred in Africans and resulted in altered RH alleles that predict partial antigens, contributing to the high rate of Rh alloimmunisation among patients with sickle cell disease (SCD). In this study, we characterised variant RH alleles encoding partial antigens and/or lacking high prevalence antigens in patients with SCD and in African Brazilian donors, in order to support antigen-matched blood for transfusion. MATERIAL AND METHODS: RH genotypes were determined in 168 DNA samples from SCD patients and 280 DNA samples from African Brazilian donors. Laboratory developed tests, RHD BeadChip(TM), RHCE BeadChip(TM), cloning and sequencing were used to determine RHD-CE genotypes among patients and African Brazilian blood donors. RESULTS: The distributions of RHD and RHCE alleles in donors and patients were similar. We found RHCE variant alleles inherited with altered RHD alleles in 25 out of 168 patients (15%) and in 22 out of 280 (7.8%) African Brazilian donors. The RHD and RHCE allele combinations found in the population studied were: RHD*DAR with RHCE*ceAR; RHD*weak D type 4.2.2 with RHCE*ceAR, RHD*weak D type 4.0 with RHCE*ceVS.01 and RHCE*ceVS.02; RHD*DIIIa with RHCE*ceVS.02. Thirteen patients and six donors had RHD-CE genotypes with homozygous or compound heterozygous alleles predicting partial antigens and/or lacking high prevalence antigens. Eleven patients were alloimmunised to Rh antigens. For six patients with RHD-CE genotypes predicting partial antigens, no donors with similar genotypes were found. DISCUSSION: Knowledge of the distribution and prevalence of RH alleles in patients with SCD and donors of African origin may be important for implementing a programme for RH genotype matching in SCD patients with RH variant alleles and clinically significant Rh antibodies.

Assuntos

RESUMO

BACKGROUND: Alloimmunisation is a major complication in patients with sickle cell disease (SCD) receiving red blood cell (RBC) transfusions and despite provision of Rh phenotyped RBC units, Rh antibodies still occur. These antibodies in patients positive for the corresponding Rh antigen are considered autoantibodies in many cases but variant RH alleles found in SCD patients can also contribute to Rh alloimmunisation. In this study, we characterised variant RH alleles in 31 SCD patients who made antibodies to Rh antigens despite antigen-positive status and evaluated the clinical significance of the antibodies produced. MATERIALS AND METHODS: RHD and RHCE BeadChip™ from BioArray Solutions and/or amplification and sequencing of exons were used to identify the RH variants. The serological features of all Rh antibodies in antigen-positive patients were analysed and the clinical significance of the antibodies was evaluated by retrospective analysis of the haemoglobin (Hb) levels before and after transfusion; the change from baseline pre-transfusion Hb and the percentage of HbS were also determined. RESULTS: We identified variant RH alleles in 31/48 (65%) of SCD patients with Rh antibodies. Molecular analyses revealed the presence of partial RHD alleles and variant RHCE alleles associated with altered C and e antigens. Five patients were compound heterozygotes for RHD and RHCE variants. Retrospective analysis showed that 42% of antibodies produced by the patients with RH variants were involved in delayed haemolytic transfusion reactions or decreased survival of transfused RBC. DISCUSSION: In this study, we found that Rh antibodies in SCD patients with RH variants can be clinically significant and, therefore, matching patients based on RH variants should be considered.

Assuntos

RESUMO

OBJECTIVE: To evaluate the usefulness of DNA methods to provide a means to precisely genotypically match donor blood units for the antigen-negative type of 35 sickle cell disease patients. METHODS: Red blood cell units were investigated for ABO, D, C, c, E, e, K, Fy(a), Fy(b), Jk(a), Jk(b), S, s, Di(a) and RH variants by performing a molecular array (Human Erythrocyte Antigen BeadChip(TM), BioArray Solutions), polymerase chain reaction followed by restriction fragment length polymorphism analysis and sequencing of patient samples and donor units that had been serologically matched based on the ABO, Rh and K phenotypes and the presence of antibodies. RESULTS: Matches for 21 of 35 sickle cell disease patients presented discrepancies or mismatches for multiple antigens between the genotype profile and the antigen profile of their serologically-matched blood units. The main discrepancies or mismatches occurred in the RH, FY, JK and MNS systems. Eight Rh alloimmunized patients presented RHD and RHCE variants that had not been serologically identified. According to these results better matches were found for the patients with genotyped units and the patients benefited as shown by better in vivo red blood cell survival. CONCLUSION: Molecular matching is superior to serological matching in sickle cell disease patients, decreasing the risk of transfusion reactions, especially delayed transfusion reactions to existing alloantibodies and preventing alloimmunization.

RESUMO

BACKGROUND: Maternal plasma analysis for the determination of the fetal RHD status is an exciting tool for the management of RhD-negative pregnant women, specially sensitized women. We assessed the accuracy of fetal RHD genotyping by analysis of maternal plasma in a multi-ethnic population. METHODS: We analyzed plasma samples from 88 RhD-negative pregnant women between 11 and 39 weeks of gestation, median age of 28 years old to determine the fetal RHD genotype. This population was from Southeastern Brazil with high mixed ethnic background. Fourteen patients (16%) had anti-D alloantibody. We used Taqman primers and probes to detect by real-time PCR, exons 4, 5, and 10 of RHD. As internal controls we used primers/probes sets to SRY and CCR5. Peripheral or umbilical cord bloods from respective neonates were collected during delivery and hemagglutination was performed. RESULTS: Fifty-eight samples (66%) were genotyped as RHD+, 27 samples (31%) showed complete absence of RHD and 3 samples (3 %) presented a D variant (RHDψ). All the results agreed with the neonatal typing, including the three fetuses with the RHDψ, phenotyped as RhD-negative. Thus, the accuracy of the fetal RHD genotyping in this mixed population was 100%. The earliest pregnancy in which fetal RHD was detected was 11 weeks. CONCLUSION: Our findings indicate that the accuracy of RHD gene using three regions (exons 4, 5, and 10) can be sufficient for clinical application in a multi-ethnic population. This knowledge helped us on the development of a feasible protocol for fetal RHD genotyping on DNA from maternal plasma for our population.

Assuntos

RESUMO

Rh discrepancies are a problem during routine testing because of partial D or weak D phenotypes. Panels of monoclonal antibodies (MoAb) are being developed to identify D variants such as partial D and weak D when there are anomalous D typing results; however, molecular characterization offers a more specific classification of weak and partial D. The weak D and partial D phenotypes are caused by many different RHD alleles encoding aberrant D proteins, resulting in distinct serologic phenotypes and the possibility of anti-D immunization. We evaluated currently used serologic methods and reagents to detect and identify D variants and correlated the results with molecular analyses. A total of 306 blood samples from Brazilian blood donors and patients with discrepant results in routine D typing were analyzed. In total, 166 (54.2%) weak D, 136 (44.4%) partial D, 3 (1%) DEL, and 1 (0.3%) DHAR variants were identified. Among weak D samples, 76 weak D type 1 (45.8%), 75 weak D type 2 (45.2%), 13 weak D type 3 (7.8%), and 2 weak D type 5 (1.2%) alleles were found. Among the partial D samples, 49 type 4.0 weak partial D (36%), 9 DAR (6.6%), 24 DFR (17.6%), 6 DBT (4.4%), 1 DHMi (0.73%), 26 DVI (19%), 14 DVa (10.3%), 5 DIVb (3.7%), and 2 DVII (1.5%) were observed. Two samples identified as DEL by adsorption-elution were characterized by molecular analyses as RHD(IVS5­38DEL4) and one sample was characterized as RHD(K409K). One sample was characterized as DHAR, a CE variant positive with some monoclonal anti-D. Our results showed that the use of different methods and anti-D reagents in the serologic routine analysis revealed D variants that can be further investigated. Molecular methods can help to differentiate between partial D and weak D and to characterize the weak D types, providing additional information of value in the determination of D phenotypes. This distinction is important for optimized management of D­ RBC units and for the prevention of anti-D­related hemolytic disease of the fetus and newborn.

Assuntos

RESUMO

OBJECTIVE: To establish the performance of conventional PCR as a noninvasive method for fetal genotyping, by free fetal DNA analysis of distinct RHD regions from maternal plasma, in a population of a diverse ethnic origin. METHODS: We conducted a validity of the diagnostic test by analyzing 81 plasma samples from RhD-negative Brazilian pregnant women, from 4 to 41 gestational weeks. We tested for exon 10 and intron 4 gene regions by allele specific-PCR. Fetal RHD genotyping by PCR on maternal plasma was compared to serologic RhD typing in the neonatal period. RESULTS: Samples were obtained as follows: 15 in the 1st, 37 in the 2nd and 29 in the 3rd trimester. General accuracy was 97.3%, sensitivity of 98.3% and specificity of 93.8%. CONCLUSIONS: Conventional PCR is an accurate method for fetal RHD genotyping on maternal plasma, even in a population of mixed ethnic origin.

Assuntos

RESUMO

The Brazilian External Quality Assessment Program in Immunohematology (BEQAPI) was introduced with the objective of evaluating the quality of diagnosis in immunohematology. From 1992 to 2003, proficiency tests for ABO grouping, Rh (D, C, c, E, e), K phenotyping, direct antiglobulin testing (DAT), antibody screening (AS), and antibody identification (AI) were performed. A total of 41 evaluations were carried out in 223 institutions. Over the period of 12 years, the program included 8,014 ABO typing, 8,000 RhD typing, 5,193 Rh typing (C, c, E, e), 5,101 K phenotyping, 7,939 AS, 4,533 AI, and 7,912 DATs. Erroneous responses were classified as clerical, technical, or undetermined. A substantial proportion of erroneous responses due to clerical errors occurred in ABO typing (76/76 errors), RhD typing (34/58 errors), and Rh phenotyping (50/73 errors). Technical errors occurred predominantly for weak D (91/95 errors), AS (252/301 errors), and AI (321/335 errors). Based on these results, since 1996, participants have received "Questions and Case Studies" in Immunohematology as an incentive for training and education. The results of the present study show an improvement in the performance of participants in the course of the program. We found that a well-organized external proficiency program can contribute to the improvement of quality of testing in Immunohematology.

Assuntos

RESUMO

We evaluated the usefulness of blood group genotyping as a supplement to hemagglutination to determine the red blood cell (RBC) antigen profile of polytransfused patients with beta-thalassemia. We selected 10 alloimmunized patients who were receiving antigen-matched RBCs based on phenotype, and had clinical evidence of delayed hemolytic transfusion reaction. DNA was prepared from blood samples and RH E/e, K1/K2, FY A/FY B, and JK A/JK B alleles were determined by PCR-RFLP. RH D/non-D was determined according to the PCR product size associated with the RHD gene sequence in intron 4 and exon 10/3'UTR. RH C/c was tested by multiplex PCR. The phenotypes and genotypes of nine of the 10 samples were discrepant. Five of the discrepancies occurred in the Rh system. One sample was phenotyped as Rhcc and genotyped as RH C/C, and two samples were phenotyped as RhCc and genotyped as RH C/C. Two other samples were phenotyped as RhEe and genotyped as RH e/e. Three samples had discrepancies in the Kidd system with phenotype Jk(a+b+) and were genotyped as homozygous for JK B. One sample had a discrepancy in the Duffy system: it was phenotyped as Fy(a+b-) and homozygous for FY B. Genotyping was very important in determining the true blood groups of many polytransfused patients with beta-thalassemia, and it assisted in the identification of suspected alloantibodies and the selection of antigen-negative RBCs for transfusion.

Assuntos

RESUMO

BACKGROUND: The usefulness of DNA genotyping for RBC antigens as a tool for the management of multiply-transfused patients with sickle cell disease (SCD) to overcome the limitations of hemagglutination assays was evaluated. STUDY DESIGN AND METHODS: Blood samples from 40 multiply-transfused SCD patients were studied by hemagglutination and by PCR-RFLP for antigens or genes in the Rh (D, C/c, E/e), Kell, Kidd, and Duffy systems. RESULTS: Discrepancies were found between hemaglutination and DNA typing test results in six patients: two were discrepant in Rh typing (one was D- by hemagglutination and RhD by DNA, and one was E+e- and RhEe by DNA), two were discrepant in Duffy typing [both were Fy(a+b-) and Fy(b)/Fy(b) by DNA], and four were discrepant in Kidd typing [Jk(a+b+) and Jk(b)/Jk(b) by DNA; two of these samples were also discrepant in Duffy]. Stored segments from blood units that had been recently transfused to these six recipients were phenotyped, confirming that the transfused RBCs were the source of the discrepancy between genotype and phenotype. CONCLUSION: DNA typing of blood groups by PCR-RFLP in peripheral blood WBCs contributes to the management of transfusions in SCD patients by allowing a more accurate selection of donor units.

Assuntos