Characterization of Blood Group Variants in an Omani Population by Comparison of Whole Genome Sequencing and Serology.

Although blood group variation was first described over a century ago, our understanding of the genetic variation affecting antigenic expression on the red blood cell surface in many populations is lacking. This deficit limits the ability to accurately type patients, especially as serological testing is not available for all described blood groups, and targeted genotyping panels may lack rare or population-specific variants. Here, we perform serological assays across 24 antigens and whole genome sequencing on 100 Omanis, a population underrepresented in genomic databases. We inferred blood group phenotypes using the most commonly typed genetic variants. The comparison of serological to inferred phenotypes resulted in an average concordance of 96.9%. Among the 22 discordances, we identify seven known variants in four blood groups that, to our knowledge, have not been previously reported in Omanis. Incorporating these variants for phenotype inference, concordance increases to 98.8%. Additionally, we describe five candidate variants in the Lewis, Lutheran, MNS, and P1 blood groups that may affect antigenic expression, although further functional confirmation is required. Notably, we identify several blood group alleles most common in African populations, likely introduced to Oman by gene flow over the last thousand years. These findings highlight the need to evaluate individual populations and their population history when considering variants to include in genotype panels for blood group typing. This research will inform future work in blood banks and transfusion services.

Seroprevalence of Human T-cell Lymphotropic Virus Types I/II Among Blood Donors in a Tertiary Hospital in Oman.

Objectives: Routine blood donor screening of human T-cell lymphotropic virus (HTLV) has been practiced in Oman since 2017. Limited data exists on HTLV seroprevalence among Omanis. This study aims to determine the seroprevalence of HTLV-I/II among blood donors attending a hospital-based blood bank to assess the need for a universal versus targeted screening. Methods: We conducted a retrospective review of blood donors' results attending a hospital blood bank between January 2017 and February 2020. Blood samples were screened for HTLV-I/II antibodies using ARCHITECT i2000SR. Reactive samples underwent further testing by immunoblot assay (MP Diagnostics HTLV Blot 2.4). Age, gender, and nationality were assessed. All components manufactured at the blood bank undergo leukoreduction before storage. Results: A total of 24 469 first-time blood donors were screened for HTLV antibodies. Most participants were male (n = 22 186, 90.7%), and the majority were Omani (n = 22 711, 92.8%). The age range was 18 to 64 years, with a median of 32 years. The seroreactivity rate was 0.2% (43; 95% CI: 0.12-0.23). Confirmatory testing by immunoblot revealed three indeterminate results (7.9%), of which two were Omani and one non-Omani donor, and the remaining 40 seroreactive donors tested negative. Conclusions: Our study revealed zero seroprevalence of confirmed HTLV among blood donors. The continuation of universal screening for first-time donors is a standard of care. With universal leukoreduction at Sultan Qaboos University Hospital and a very low risk of HTLV in Oman's population, the need for screening regular donors can be reconsidered if these findings are confirmed on a larger scale involving other blood banks in Oman.

Molecular blood group screening in Omani blood donors.

BACKGROUND AND OBJECTIVES: Blood group genotyping has been used in different populations. This study aims at evaluating the genotypes of common blood group antigens in the Omani blood donors and to assess the concordance rate with obtained phenotypes. MATERIAL AND METHODS: Blood samples from 180 Omani donors were evaluated. Samples were typed by serological methods for the five blood group systems MNS, RH (RHD/RHCE), KEL, FY and JK. Samples were genotyped using RBC-FluoGene vERYfy eXtend kit (inno-train©). Predicted phenotypic variants for 70 red blood cell antigens among the MNS, RH (RHD/RHCE), KEL, FY, JK, DO, LU, YT, DI, VEL, CO and KN blood group systems were assessed. RESULTS: Simultaneous phenotype and genotype results were available in 130 subjects. Concordance rate was >95% in all blood group systems with exception of Fy(b+) (87%). Homozygous GATA-1 mutation leading to erythroid silencing FY*02N.01 (resulting in the Fy(b-)ES phenotype) was detected in 81/112 (72%) of genotyped samples. In addition, discrepant Fyb phenotype/genotype result was obtained in 14/112 samples; 13 of which has a heterozygous GATA-1 mutation and one sample with a wild GATA genotype. D and partial e c.733C>G variants expressing the V+VS+ phenotype were found in 22/121 (18.2%) and 14/120 (11.7%) of the samples, respectively. Di(a-b+), Js(a-b+), Yt(a+b-) and Kn(a+b-) genotype frequencies were 99.4%, 95.8%, 91.9% and 97.7%, respectively. CONCLUSION: In conclusion, we report a high frequency of FY*02N.01 allele due to homozygous c.-67T>C GATA-1 single-nucleotide variation. This is the first study reporting the detailed distribution of common and rare red cell genotypes in Omani blood donors.

Prevalence of Red Blood Cell Major Blood Group Antigens and Phenotypes among Omani Blood Donors.

OBJECTIVES: Most literature on the frequencies of red blood cell (RBC) phenotypes are published in Europeans and Africans countries, with the frequencies in the Omani population unknown. We sought to determine the prevalence of RBC blood group phenotypes among Omani blood donors. METHODS: Blood group ABO, RhD type, and phenotyping were performed for 21 blood group antigens on enrolled blood donors. The following antigens were assessed serologically: Rh (C, c, E, e), Kell (K, k, Kpa, Kpb), Kidd (Jka, Jkb), Duffy (Fya, Fyb), Lewis (Lea, Leb), Lutheran (Lua, Lub), MNS (M, N, S, s), and P1. RESULTS: A total of 337 Omani blood donors were tested. The most common blood group was O+ (44.9%). Among the tested blood donors studied, 89.3% were RhD positive with R1r being the most common Rh phenotype. The k antigen was found at a frequency of 99.4%, while 4.5% of the blood donors studied were K+. The most common phenotype in the Duffy blood group system was Fy(a-b-), while the most common phenotypes in the Kidd and MNS blood group systems were Jk(a+b+) and M+N-S+s+ at 47.0% and 22.6%, respectively. The Le(a+) and Le(b+) antigens were found in 21.7% and 67.3% of the blood donors, respectively. One Jk(a-b-), one Le(a+b+), and two Lu(a-b-) individuals were identified. CONCLUSION: This is the first study to examine the frequencies of RBC phenotypes among the Omani blood donors. The study's results show Duffy blood group frequencies that resemble what has been reported in the African population, and higher frequencies of the rare null phenotypes compared to European populations.

Intrauterine Fetal Blood Transfusion: Descriptive study of the first four years' experience in Oman.

OBJECTIVES: Haemolytic disease of the fetus and newborn (HDFN) causes hydrops fetalis. The successful treatment of HDFN has been reported with intrauterine blood transfusion (IUT). This study aimed to describe the initial experience with IUT procedures in Oman. METHODS: This retrospective observational study took place at the Royal Hospital and Sultan Qaboos University Hospital Blood Bank, Muscat, Oman, and included all women who underwent IUT procedures in Oman between March 2012 and March 2016. Gestational and neonatal outcomes were assessed, including complications, morbidity, neurodevelopmental sequelae and mortality. RESULTS: A total of 28 IUT procedures for 13 fetuses carried by 11 women were performed. Gestational age at the time of referral ranged from 13-30 weeks, while the median gestational age at first IUT procedure was 26 weeks (range: 19-30 weeks). Indications for the procedure included HDFN caused by anti-D (n = 6), a combination of anti-D and anti-C (n = 4), anti-K (n = 1) and anti-Jsb (n = 1) antibodies and nonimmune hydrops fetalis due to a congenital parvovirus infection (n = 1). Median fetal haemoglobin levels at the beginning and end of the procedure were 4.6 g/dL and 12.8 g/dL, respectively. Most procedures were transplacental intravascular transfusions through the placental umbilical cord root (71.4%), followed by transamniotic intravascular transfusions (14.3%). The overall survival rate was 61.5%, with five deaths; of these, four were intrauterine and one was an early neonatal death due to non-resolved hydrops and severe cardiac dysfunction. CONCLUSION: As a relatively novel obstetric procedure in Oman, IUT seems to result in a favourable outcome for hydropic fetuses.

Risks of red blood cell alloimmunization in transfusion-dependent ß-thalassemia in Oman: a 25-year experience of a university tertiary care reference center and a literature review.

BACKGROUND: ß-Thalassemia is a common hemoglobinopathy in the Arabian Peninsula. Red blood cell (RBC) transfusion is a cornerstone for its management, but can create significant challenges including RBC alloimmunization. Herein, we examine alloimmunization risk factors in Omani patients with transfusion-dependent ß-thalassemia. Existing literature is summarized. STUDY DESIGN AND METHODS: A retrospective review of all patients attending our center over 25 years was performed. Clinical and transfusion records were examined. Chi-square test was used to assess the association between the categorical variables. Nonparametric Mann-Whitney test was used to assess the association between transfusion and risk of alloimmunization. RESULTS: A total of 268 patients were identified (168 adults and 100 pediatrics), of whom 226 are alive (84.3%). Males accounted for 53.4%. The cohort had a median age of 22 years (range, 2-43 years). The most common blood group was O+ (39%). The prevalence of alloimmunization was 9.3% with anti-E (24%) and anti-K (24%) being the commonest antibodies identified. There was a significant association between age and alloimmunization, with 68% of alloimmunized patients in the age group of 19 to 30 years (p < 0.01). Among adults, there was a significant association between alloimmunization and number of units transfused (p = 0.001). There was no association between alloimmunization and sex or history of splenectomy. CONCLUSION: Our study shows an association between alloimmunization and the age of the patients and number of units transfused. Transfusion support of this group of patients necessitates the availability of needed expertise and blood bank facilities.