تعیین ساختار ژنتیکی و فنوتیپی گویچه قرمز در شیوه آزمایشگاهی
Abstract
1- Introduction
2- Materials and methods
3- Results
4- Discussion
5- Conclusion
References
Abstract
False-positive and false-negative reactions exist for serological and molecular antigen typing methods. If the predicted phenotype is inconsistent with the patient`s known antibodies or serological phenotype, the discrepancy must be investigated. False-negative and false-positive results are clinically problematic in blood donors and patients. In this study, we investigated discrepant results between serology and molecular testing in patients and blood donors that occurred in daily molecular laboratory practice over a two year-period. SCD patients represented a large percentage of our cases of discrepancies but we also observed a high prevalence of discrepancies between phenotypes and genotypes in blood donors. The main reasons that led to discrepancies were recent transfusions and limitations of phenotyping. Discrepancies classified as false positive phenotype/true negative genotype and false negative phenotype/true positive genotype occurred mainly in patients with recent transfusions and individuals with RH variants while those classified as true negative phenotype/false positive genotype involved null phenotypes due to silent genes. Despite the limitations of molecular methods currently employed, we found more false-negative and false-positive phenotypes than genotypes demonstrating that genotyping is more efficient to define the blood types, especially in transfusion dependent patients.
Introduction
Hemagglutination has been used to determine red blood cell (RBC) types and has been considered the gold standard for over a century [1]. However, technical and clinical limitations of serologic immunohematology have led many laboratories to the use of molecular assays to predict red cell phenotype [2]. The characterization of the genes encoding the 36 blood group systems recognized by the Working Party on Red Cell Immunogenetics and Blood Group Terminology of the International Society of Blood Transfusion (ISBT) [3] and the knowledge of the molecular events that give rise to blood group antigens and phenotypes [4] have made possible the application and implementation of molecular testing into blood centers, reference laboratories and transfusion services [2,5]. Low-, medium- and high-throughput techniques have been developed for blood group genotyping and in the last decade we have seen a great expansion and evolution of the technologies available [6–12]. Thus, molecular testing is rapidly advancing and offers tremendous help as a powerful tool with potential advantages in the identification of rare RBC donors and finding antigen matches for chronically transfused patients [7,13–17]. However, it should be noted that, regardless of the test protocols used, genotyping predicts a blood type but does not determine the phenotype the way serologic tests do. In some instances, the genotype will not correlate with the phenotype because the simple presence of a gene does not mean that the gene will be expressed as an antigen on the RBC membrane. A large number of genetic events may silence or weaken the expression of antigens encoded by an allele [4]. There are several examples of misleading results of molecular typing in the literature, but there is a consensus that molecular typing test is an invaluable supplement to traditional serological method and these tests are likely to become essential, rather than optional, for blood donor and patient testing [15,16]. Thus, the profile of a gene needs to be completely elucidated, and appropriate assays need to be performed to look for genetic changes that may alter the predicted phenotype.