HLA-B Allelic Distribution in Samples from Thailand National Health Examination Survey (การกระจายตัวของ HLA-B อัลลีลในตัวอย่างจากโครงการสำรวจสุขภาพประชาชนไทยยครั้งที่ 3)

HLA-B allele is a clinically relevant genetic marker in pharmacogenomics. Carrier status of at risk allele is useful information for avoidance of serious cutaneous adverse reactions. Therefore information of regional allelic distribution of HLA-B in Thailand is essential for consideration processes for adoption of the genetic testing to avoid drug induced severe cutaneous adverse reaction (SCAR), including Steven Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). This study reported the distribution of HLA-B alleles in 650 samples, which were randomly sampled from the 3rd Thailand National Health Examination Survey to represent population of 4 regions and the capital city, Bangkok. It was found that the HLA-B *15:02 allele, associated with carbamazepine induced of SJS/TEN, was detected at highest prevalence in Bangkok (10.00%) and the southern region (9.50%). The frequency of HLA-B*15:02 allele in northeast, north, and central were 7.33%, 8.39% and 9.25%, respectively. The HLA-B*58:01, associated with allopurinol induced SJS/TEN was the most frequent allele found in the northeast area (9.00%) and Bangkok (9.00%) but its frequency was low in the northern (6.38%), central (5.00%) and southern area (4.50%). In contrast, the HLA-B*35:05 allele, associated with nevirapine induced rash, was most commonly found in the southern area (4.00%) and less common in the northeast (3.33%), central (2.25%), Bangkok (2.00%) and northern areas (0.67%). These results indicated that the distributions of HLA-B alleles are different in each region of Thailand, which may depend on the pattern of ancestral migration. The data on the distribution of HLA-B alleles from major geographic regions of Thailand are useful information for policy adoption of pharmacogenomics testing services in Thailand. Key words: HLA-B allele, Thai population, pharmacogenomics, severe cutaneous adverse reaction