Search

Background: Recent retrospective studies indicate that D- recipients of D+ apheresis platelets (PLTs) are not alloimmunized to D. Our hospital policy is to offer RhIG to D- women of childbearing age who received D+ apheresis PLTs but not to other D- recipients of D+ apheresis PLTs. We instituted prospective surveillance of the D- recipients who were not given RhIG., Study Design and Methods: All apheresis PLT recipients were prospectively entered into a database that recorded the patient's age, sex, diagnosis, D status, apheresis PLT transfusions, and antibody screen results from before and after PLT transfusions. Data are reported for PLTs transfused between October 16, 2012, and April 16, 2014, and antibody screens obtained through June 16, 2014. The analysis excludes neonates; women not more than 50 years of age; and patients who also received D+ red blood cells, received only D- PLTs, received RhIG, were previously alloimmunized to D, and did not have a follow-up antibody screen after the first D-incompatible apheresis PLT transfusion., Results: A total of 158 of 1107 apheresis PLT recipients were D-. Seventy-nine were eligible for analysis based on the exclusion criteria listed above. None became alloimmunized to D during the observation interval. In 45 (57%) cases the last follow-up antibody screen was obtained at least 4 weeks after the first D-incompatible apheresis PLT transfusion., Conclusion: Prospective surveillance confirms prior retrospective observations that D- patients do not appear to risk D alloimmunization after receiving D+ apheresis PLTs., (© 2014 AABB.)

Background: Weak D types are thought to express rather quantitative than qualitative D antigen variants. Distinct type-specific phenotypes and weak D cases with anti-D alloimmunization, however, suggest a variable degree of D antigen alteration., Study Design and Methods: Variant D types were investigated by use of molecular typing, RHD sequencing, extended serologic D antigen investigations, and flow cytometric D antigen density determination., Results: Two novel weak D types were discovered, termed weak D type 31 and 32 with single RHD nucleotide substitutions coding for amino acid exchanges in predicted intracellular RhD polypeptide stretches, with antigen densities of approximately 130 and 50 D sites per red blood cell, respectively. Adsorption-elution technique-supported D epitope mapping of these two weak D types, the recently described weak D type 26, and of the most common Central European weak D types (weak D types 1, 2, 3, 4.0, and 4.1) demonstrated the expression of all tested D epitopes. In contrast, a distinct D epitope loss was detected in weak D type 15 and partial D control samples., Conclusion: All novel and prevalent weak D types expressed all tested D epitopes. Our results indicate that adsorption-elution techniques may be of advantage whenever D epitope loss is suspected in extremely weak D variants.

Background: The D antigen of the polymorphic Rh blood group system is of particular clinical importance regarding transfusion- and pregnancy-induced alloimmunization. Different RhD variants with specific clinical implications have been characterized. The least expressed D variants collectively called DEL are serologically detectable only by adsorption-elution techniques, with so far only poorly defined antigenic properties., Study Design and Methods: A comprehensive immunohematologic analysis of five of the six currently known DEL genotypes was performed. DEL phenotypes associated with the RHD(M295I), RHD(IVS3+1g>a), RHD(K409K), RHD(X418L), or RHD(IVS5-38del4) allele were characterized with extended serology and flow cytometry., Results: Epitope mapping with adsorption-elution revealed a prominent D epitope loss in the RHD(IVS3+1g>a)-associated DEL phenotype, whereas in the other four DEL types no signs of qualitative D antigen alteration were detected. The observation of alloanti-D in two RHD(IVS3+1g>a) cases confirmed the partial nature of this DEL phenotype. The RHD(M295I) phenotype exhibited the highest D antigen expression among all investigated DEL types, as determined by a semiquantitative adsorption-elution approach and flow cytometry., Conclusion: In conclusion, evidence is provided that different DEL genotypes code either for partial or complete D antigen expression and that this finding is clinically relevant.

Background: The D antigen includes category D, partial D, and weak D types, which are important because anti-D alloimmunization can occur in some but not all persons that express a variant RHD allele. At present, there is little prospective information on the prevalence of D variants among obstetric patients and potential transfusion recipients., Study Design and Methods: The RHD alleles were prospectively examined in a large patient population identified on the basis of a difference in anti-D reactivity between two reagents., Results: Fifty-five discrepancies (0.96% of D-) were noted among 33,864 ethnically diverse patients over 18 months, of which 54 represented mutated RHD alleles. Seven obstetric patients were assigned D- status based on serology; only 1 patient had a partial RHD allele. Ten of 25 (36%) obstetric patients and 4 of 6 (67%) female potential transfusion recipients of childbearing age or younger were assigned D+ status, and they expressed a D variant known to permit anti-D alloimmunization. In total 20 RHD alleles were identified including category, DVa or DVa-like alleles (n = 7), DAR (n = 8), and four novel RHD alleles including two new DAU alleles., Conclusion: Given the complexity of D antigen expression, it is concluded that some clinically important D variants identified by standard serologic analysis phenotype as D+ and are potentially at risk for the development of anti-D.

Background: Recent molecular studies of the RHD gene have revealed that D(el) individuals retain a grossly intact RHD gene or have a portion of RHD in their genomes. No D(el) phenotype has yet been shown to induce a primary or secondary alloanti-D immunization, however., Case Report: A 67-year-old D- Japanese woman with a history of allosensitization from transfusion of D+ red blood cells (RBCs) was negative for anti-D at admission. After she received RBCs from 19 apparently D- donors, she developed anti-D with an 8-fold titer. The titer of anti-D increased further to 128-fold after transfusions of cross-match-compatible D- negative RBCs from 40 donors over the next 2 years. Two of 59 donors were found to be RHD gene-positive and antigen D- with a D(el) phenotype, that is, RHD(K409K)., Conclusion: This is the first case in which RBCs having the D(el) phenotype induced a secondary alloanti-D immunization. A D- donor with the RHD(K409K) allele was associated with the development of anti-D. Adverse episodes or evidence of hemolysis was not observed after the transfusion of RHD(K409K) RBCs. Further clinical evidence is needed to reveal whether the D(el) phenotype has a clinically relevant potential for anti-D immunization.

Background: Thalassemia major is a common hemoglobinopathy in the Arabian Gulf region. However, limited data are available on the frequency of RBC alloimmunization and autoimmunization in transfusion-dependent Arab thalassemia patients., Study Design and Methods: A total of 190 thalassemia major patients were classified as Kuwaiti Arab and non-Kuwaiti Arab. Pretransfusion investigation records were reviewed for the presence of RBC alloantibody and autoantibody, and the age at which RBC alloantibody was developed., Results: Fifty-seven (30%) patients developed RBC alloantibodies. The most common clinically significant alloantibodies were directed against antigens in the Kell and Rh systems. Anti-K developed in 41 (72%) patients followed by anti-E in 26 (45.6%). RBC autoantibodies developed in 21 (11%) patients with and without underlying RBC alloantibodies. Sixty-six (49.6%) RBC alloantibodies developed between the ages of 2 and 10 years., Conclusion: Several factors might have contributed to the high alloimmunization and autoimmunization rate observed in this study, including the heterogeneity of the population living in Kuwait, lack of better-matched donors for those patients, and the use of poststorage leukodepleted blood. It is recommended that thalassemia patients receive blood matched for Rh and Kell antigens and prestorage leukodepleted RBCs.

Appropriate postpartum administration of Rh immune globulin relies on sensitive detection and accurate quantitation of fetomaternal hemorrhage (FMH). Recently, the microscopic Du test (micro Du) enhanced with polyethylene glycol (PEG Du) and flow cytometry (FC) have been advocated for this purpose. Three qualitative methods (micro Du, rosette test, and PEG Du) and two quantitative methods (acid elution and FC) for assessing FMH were evaluated with particular attention given to PEG Du and FC. In vitro studies comprised 10 series of dilutions of D+ cord cells in D- adult cells to yield D+ cell concentrations of 0.06, 0.12, 0.25, 0.50, 0.75, 1.0, and 2.0 percent. Additionally, 26 postpartum samples were tested. Of the qualitative techniques, the micro Du test was the least sensitive with 20 percent false-negative results occurring at 0.5 percent fetal cells. The PEG Du test was only slightly more sensitive and offered no clinical advantage. The rosette test was the most sensitive, consistently detecting fetal cells at concentrations of 0.25 percent or greater. FC and acid elution showed similar results, with good correlation obtained between measured and expected quantities of fetal cells (r = 0.99 and 0.96, respectively). One of 26 postpartum samples was positive by all screening techniques; acid elution and FC detected 0.3-percent concentrations of fetal cells and 0.17-percent concentrations of D+ cells, respectively. Although acid elution is a more commonly used method for quantitating FMH, FC offers an acceptable alternative that is capable of analyzing large numbers of cells with objectivity and reproducibility.