Bilirubin concentrations in thalassemia heterozygotes in university students

To investigate the difference of bilirubin concentrations between α- and β-thalassemia carriers and the role of variation status in the UDP-glucuronosyltransferase (UGT) 1A1 gene on such a difference.

A total of 2713 university freshmen who attended a regular physical examination were enrolled in underwent screenings for thalassemias. Finally, 123 subjects whose mean corpuscular volume was ≤80 fL and who had no iron deficiency anemia were tested by PCR and PCR-restriction fragment length polymorphism (RFLP) for α- and β-thalassemias, respectively, and tested by PCR-RFLP for the five known variations of the UGT1A1 gene.

Among the 123 subjects, 76 and 47 were diagnosed with heterozygous α-thalassemia and with heterozygous β-thalassemia, respectively. Between the α- and β-thalassemia heterozygotes, variation status of the UGT1A1 gene was not statistically different (P = 0.898), while hemoglobin and bilirubin concentrations differed significantly (P = 0.005 and 0.001, respectively). Bilirubin concentrations were significantly higher among individuals with compound heterozygous variations/homozygous variation in the UGT1A1 gene than in those possessing the wild type and heterozygous variation (P < 0.001 for both α- and β-thalassemia heterozygotes). Compound heterozygous variations/homozygous variation in the UGT1A1 gene and anemia were the main causes of hyperbilirubinemia in α- and β-thalassemia heterozygotes, respectively.

The difference in bilirubin concentrations between α- and β-thalassemia heterozygotes may be attributable to more bilirubin being produced in β-thalassemia heterozygotes than in α-thalassemia heterozygotes, while variation status of the UGT1A1 gene affects bilirubin concentrations in both α- and β-thalassemia heterozygotes.