Erythrocyte indices in a large cohort of β‐thalassemia carrier: Implication for population screening in an area with high prevalence and heterogeneity of thalassemia

Abstract Introduction Most β‐thalassemia carriers have hypochromic microcytosis with mean corpuscular volume (MCV) < 80 fL and mean corpuscular hemoglobin (MCH) < 27 pg. These can be variable due to β‐thalassemia mutations, genetic interaction between thalassemic genes, and blood cell counters. We have examined whether these indices are effective in screening of β‐thalassemia in Thailand where thalassemia is prevalence and heterogeneous. Methods Retrospective data were reviewed on 11 443 Thai subjects encountered from August 2014 to August 2017. Subjects with heterozygous β‐thalassemia based on Hb and DNA analyses were recruited along with MCV and MCH values and analyzed. Results Among the 11 443 subjects reviewed, 1425 were β‐thalassemia carriers. Data were available on 1214 subjects for MCV and 965 subjects for MCH. DNA analysis identified 20 different β 0 ‐thalassemia mutations in 874 (72.0%) cases and 6 β + ‐thalassemia mutations in 340 (28.0%) subjects. Of these 1214 carriers, 26 (2.1%) had MCV ≥ 80 fL; 6 (23.1%) carried β 0 ‐thalassemia, and the remaining 20 (76.9%) had β + ‐thalassemia. In contrast for those having MCH values, only 4 of 965 (0.4%) had MCH ≥ 27 pg. DNA analysis identified both β 0 ‐thalassemia and β + ‐thalassemia mutations. Conclusions Using MCV alone for the screening of β‐thalassemia may pose a significant number of false negative although three‐quarter of them are carriers of mild β + ‐thalassemia. MCH with approximately five times more sensitive is a better screening marker. Using a combined MCV and MCH is highly recommended, especially in an area with high prevalence and heterogeneity of thalassemia like Thailand.