Use

HLA‑B*58:01 typing identifies presence of the HLA‑B*58:01 allele, which is strongly associated with severe cutaneous adverse drug reactions (SCAR) when patients are treated with allopurinol. Clinical Pharmacogenomic Implementation Consortium (CPIC) guidelines recommend genotyping before allopurinol initiation and advise against the drug in patients positive for the allele. The allele frequency varies by ethnicity (≈6–7% in Asians, ~1% in Caucasians), and rheumatology guidelines recommend testing among high‑risk groups such as Han Chinese, Thai, and Koreans with advanced chronic kidney disease.