RHCE variant alleles and risk of alloimmunization in Brazilians.

Variant RHCE alleles are found mainly in Afro-descendant individuals, as well as in patients with sickle cell disease (SCD). The most common variants are related to the RHCE*ce allele, which can generate partial e and c antigens. Although RHCE variant alleles have been extensively studied, defining their clinical significance is a difficult task. We evaluated the risk of RhCE alloimmunization as a consequence of partial antigens in patients with a positive phenotype transfused with red blood cell (RBC) units with the corresponding antigen. A retrospective study was performed with Brazilian patients, evaluating the number of antigen-positive transfused RBC units (incompatible due to partial antigen) in 27 patients with SCD carrying RHCE variant alleles who did not develop antibodies as well as evaluating the variants present in 12 patients with partial phenotype and correlated antibody (one patient with SCD and 11 patients with other pathologies). Two patients showed variant alleles with molecular changes that had not yet been described. Variant RHCE alleles were identified in a previous study using molecular methods. RHCE*ceVS.01 was the most frequent allele found among the patients without antibodies. Six patients with partial c antigen had a mean of 3.8 c+ RBC units transfused, and 10 patients with partial e antigen were exposed for a mean of 7.2 e+ RBC units. Among the variant alleles found in alloimmunized patients, the most frequent was RHCE*ceAR, which was found in five patients; the antibodies developed were anti-hrS and/or anti-c. Our results showed that RHCE*ceVS.01 is indeed the most frequent variant allele in our cohort of patients with SCD, but the partial antigens that were identified have low risk of alloimmunization. RHCE*ceAR is the most impactful variant in the Brazilian population with high risk of alloimmunization and clinically significant anti-hrS formation.

Signal to cut-off (S/CO) ratio and detection of HCV genotype 1 by real-time PCR one-step method: is there any direct relationship?

BACKGROUND: Polymerase chain reaction (PCR) methods play an essential role in providing data related to diagnosis, monitoring and treatment of hepatitis C virus (HCV) infection. EIA results are reported as ''reactive'' or ''non reactive'' and EIA S/CO ratio may also be reported as ''high'' or ''low.'' This study aimed to evaluate the performance of a real-time RT-PCR and assess whether there is relationship between S/CO and PCR results. STUDY DESIGN AND METHODS: Sera from blood donors were analyzed by Enzyme-Linked Immunosorbent Assay (ELISA) and RT-PCR assay to detect HCV infection. RESULTS: The RT-PCR assay to genotypes 1a/b showed an acceptable linear response in serial dilutions. The samples were divided into two groups based on their serological results: group A--S/CO ratio < 3 (60 samples) and group B--S/CO ratio > 3 (41 samples). Viral loads were confirmed positive in group B samples in 90%, and in group A samples were confirmed positive in only 13% by RT-PCR. CONCLUSION: The methodology used was able to detect the presence of RNA-HCV genotype I in 90% of the samples serologically positive in group B. All negative samples were sent to search for other genotypes of HCV (genotypes 2-6) and were confirmed as negative. These data suggests that these negative samples may have HCV RNA viral load below the detection limit of our test (310 IU/ mL), or a false positive result in serological test, or spontaneous viral clearance occurred.