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Screening for β -thalassemia trait (BTT) relies on measuring hemoglobin (Hb) A2. Since multiple factors can affect HbA2 levels, the screening can become unreliable. In 1356 healthy Arabs enrolled into a federally funded premarital BTT screening program, the effects of iron deficiency (ID), α (+)-thalassemia trait, gender, smoking, and tribalism on HbA2 were studied. The complete blood count and hemoglobin fractions were determined on the entire cohort; serum ferritin (<15  μ g/L) in 391 subjects was used to determine ID. BTT was present in 29 (2.1%) subjects (HbA2 > 3.5%). Among 77(20.3%) subjects with ID, the mean HbA2 (2.30 ± 0.23%) was 0.2% lower than in subjects without iron deficiency (2.50 ± 0.24%, P < 0.0001). In 65 (38%)/172 subjects with phenotypic α (+)-thalassemia trait, the mean HbA2 (2.43 ± 0.24%) was 0.13% lower than in subjects without α (+)-thalassemia trait, P < 0.0001. The mean HbA2 did not differ between males and females, smokers and nonsmokers, and between the tribes. Thus, 35 (2.6%) subjects with HbA2 between 3.2 and 3.5% were at a risk of false negative diagnosis of BTT. Since iron deficiency and α (+)-thalassemia are both common and both lower HbA2, modifications in screening recommendations for BTT are proposed.

Background: Interpreting the erythroid lineage in populations with high frequency of α+ thalassemia allele is challenging due to the high prevalence of α+ thalassemia homozygotes. For such populations, separate reference values for normal and α+ thalassemia homozygotes are needed., Methods: We studied the erythroid lineage in 1,079 citizens of United Arab Emirates (UAE). Subjects with abnormal hemoglobin (39), iron deficiency (136) or erroneous entries (8) were excluded. MCV distribution in the remaining individuals (896) was visibly bimodal. Statistical mixture analysis with Normix program was used to separate subpopulations with normal and small red cells. Hardy-Weinberg equation was used to estimate genotype frequencies., Results: MCV of 78.0 fl separated phenotype-derived normal homozygotes (715) from phenotype-derived α+ thalassemia homozygotes (181). The erythrocyte indices were significantly different between the two groups (p < 0.0001). The overall prevalence of phenotype-derived α+ thalassemia homozygotes (-α/-α) was 0.20 and markedly varied among tribes, 0 to 0.31 (Mean = 0.15). The frequency of phenotype-derived α+ thalassemia allele was 0.44; when accounting for tribal population structure and inbreeding, the calculated frequency was 0.34. These values were very similar to those found in the same population by genotyping and other phenotyping methods. The erythrocyte reference values for phenotype-derived normal homozygotes in Emiratis closely overlapped with those for Caucasians and normal homozygotes defined by genotyping. The reference values for phenotype-derived α+ thalassemia homozygotes in Emiratis also closely overlapped with those for α+ thalassemia homozygotes defined by genotyping., Conclusion: In populations with frequent α+ thalassemia mutations, two sets of erythrocyte reference values could be determined without genotyping.

Background: Benign neutropenia, i.e., neutropenia not associated with an increased risk of infection, may result in serious medical consequences when a 'standard' definition of neutropenia (absolute neutrophil count (ANC) < 1.5 x 10(9)cells/L) is universally applied to all races. The aims of this study were to determine the prevalence of benign neutropenia among healthy Arabs and evaluate its mode of inheritance., Methods: ANCs were studied prospectively amongst a healthy indigenous population (n = 1032) from the United Arab Emirates undergoing a nation-wide sickle-cell and thalassemia screening program. The mean neutrophil count and the prevalence of benign neutropenia were compared by age, sex and amongst various tribes., Results: The mean neutrophil count (x 10(9)cells/L) was 3.3 (range 0.95-7.6). Benign neutropenia was present in 110 (10.7%) subjects of whom 24 (2.3%) individuals had moderate neutropenia (ANC 0.5 - 1.0 x 10(9) cells/L). In the 22 tribe-family groups, the prevalence of benign neutropenia varied between 0% and 38%. Benign neutropenia showed no difference in the frequency amongst the sexes (p = 0.23) and it was independent of age (Spearman's rho = 0.05, p = 0.13). The age-related mean neutrophil count was the lowest in Arabs when compared with other ethnic groups (Blacks, Europeans and Mexicans). The inheritance of benign neutropenia was consistent with an autosomal dominant pattern; however, the diversity of observed phenotypes suggested the presence of more than one genetic variant for this trait., Conclusion: Arabs have a high prevalence of benign neutropenia that may be inherited as an autosomal dominant trait.