Background: Interpreting the erythroid lineage in populations with high frequency of a+ thalassemia allele is\r\nchallenging due to the high prevalence of a+ thalassemia homozygotes. For such populations, separate reference\r\nvalues for normal and a+ thalassemia homozygotes are needed.\r\nMethods: We studied the erythroid lineage in 1,079 citizens of United Arab Emirates (UAE). Subjects with abnormal\r\nhemoglobin (39), iron deficiency (136) or erroneous entries (8) were excluded. MCV distribution in the remaining\r\nindividuals (896) was visibly bimodal. Statistical mixture analysis with Normix program was used to separate\r\nsubpopulations with normal and small red cells. Hardy-Weinberg equation was used to estimate genotype\r\nfrequencies.\r\nResults: MCV of 78.0 fl separated phenotype-derived normal homozygotes (715) from phenotype-derived a+\r\nthalassemia homozygotes (181). The erythrocyte indices were significantly different between the two groups (p <\r\n0.0001). The overall prevalence of phenotype-derived a+ thalassemia homozygotes (-a/-a) was 0.20 and markedly\r\nvaried among tribes, 0 to 0.31 (Mean = 0.15). The frequency of phenotype-derived a+ thalassemia allele was 0.44;\r\nwhen accounting for tribal population structure and inbreeding, the calculated frequency was 0.34. These values\r\nwere very similar to those found in the same population by genotyping and other phenotyping methods. The\r\nerythrocyte reference values for phenotype-derived normal homozygotes in Emiratis closely overlapped with those\r\nfor Caucasians and normal homozygotes defined by genotyping. The reference values for phenotype-derived a+\r\nthalassemia homozygotes in Emiratis also closely overlapped with those for a+ thalassemia homozygotes defined\r\nby genotyping.\r\nConclusion: In populations with frequent a+ thalassemia mutations, two sets of erythrocyte reference values could\r\nbe determined without genotyping.
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