Identification of the β thalassemia allele β -50 and analysis of the hematology data of carriers in a southern Chinese population.

During a routine test, we identified a 38-year-old man who had a positive hematology screening result but was negative for hot spot variants of his thalassemia gene. Further analysis identified β ^-50 (HBB: c.-100G>A). It was first suggested that β ^-50 was a β ⁺ -thal allele, and some research groups suggested this allele was a silent β-thal allele. To fully understand the hematological phenotype of the β ^-50 allele, we screened for individuals carrying β ^-50 in the general population and performed hematology analysis on these carriers. A real-time PCR detection system was designed to verify samples carrying β ^-50 . Twenty-one thousand samples and 43 pedigree samples were screened, and 86 β ^-50 carriers were detected. We performed hematological analysis on 65 individuals older than 3 years who had normal serum ferritin and analyzed the data. A total of 34.62% of the β ^-50 /β ^N individuals had mean cellular volume (MCV) or mean cellular hemoglobin (MCH) values slightly lower than the positive cutoff value of screening; the β ^-50 carriers' Hb A ₂ value was slightly elevated. According to the test results, β ^-50 carriers have slight changes in hematology parameters, including slight decreases in MCV and MCH and slight increases in Hb A ₂ ; however, these effects do not reach the degree of traditional β ⁺ alleles. Females with genotype β ^-50 /β ⁰ show a degree of decline in hematological indicators during pregnancy. Therefore, we should describe β ^-50 as a β ⁺⁺ thalassemia allele, and identification of β ^-50 can explain slight changes in hematological indicators in some carriers.
(© 2021 John Wiley & Sons Ltd/University College London.)