Thalassemia and Hemoglobin E in Southern Thai Blood Donors

Table 4

Number of risk alleles and risk allele frequency in Southern Thai blood donors.

Diagnosis	𝛼-Globin and 𝛽-globin genotypes	Number of alleles*	Number of risk alleles; (risk allele)
Normal, heterozygous 𝛼-thalassemia 2, and; homozygous 𝛼-thalassemia 2 (𝑛=103)	𝛼𝛼/𝛼𝛼, −𝛼/𝛼𝛼, −𝛼/−𝛼, and 𝛽^A/𝛽^A	412	0
Heterozygous 𝛼-thalassemia 1 (𝑛=2)	- -^SEA/𝛼𝛼, 𝛽^A/𝛽^A	8	2 (- -^SEA)
Heterozygous 𝛽-thalassemia without 𝛼-; thalassemia (𝑛=1)	𝛼𝛼/𝛼𝛼, 𝛽^0/+/𝛽^A	4	1 (𝛽^0/+)
Heterozygous Hb E without 𝛼-thalassemia; (𝑛=6)	𝛼𝛼/𝛼𝛼, 𝛽^E/𝛽^A	24	6 (𝛽^E)
Double heterozygotes for Hb E/𝛼-; thalassemia 1 (𝑛=2)	- -^SEA/𝛼𝛼, 𝛽^E/𝛽^A	8	4 (2 * 𝛽^E and 2 * - -^SEA)
Homozygous Hb E with and without; heterozygous 𝛼-thalassemia 2 (𝑛=2)	−𝛼/𝛼𝛼, 𝛼𝛼/𝛼𝛼, and 𝛽^E/𝛽^E	8	4 (𝛽^E)
Total (𝑛=116)		464	17
Risk allele frequency = 17/464 * 100 = 3.7%

- -^SEA: 𝛼-thalassemia 1 allele with Southeast Asian type deletion; 𝛽^0/+: 𝛽⁰ or 𝛽⁺-thalassemia allele with uncharacterized 𝛽-globin gene mutation; 𝛽^A: normal 𝛽-globin gene; 𝛽^E: Hb E allele.
∗The number of alleles was calculated from two alleles of 𝛼-globin genotype (𝛼𝛼/𝛼𝛼) and two alleles from 𝛽-globin genotype (𝛽/𝛽) [4 alleles were considered per one donor].