Use

This pharmacogenomic test interrogates the thymine‑adenine (TA) repeat in the TATA‑box promoter region of UGT1A1 and evaluates the UGT1A1*6 (c.211G>A) allele. Variability in TA repeat counts (TA5–TA8) affects UGT1A1 enzymatic activity. Individuals with TA7, TA8, or compound heterozygous configurations exhibit reduced activity associated with Gilbert syndrome or increased risk of adverse drug reactions, especially to irinotecan and other UGT1A1‑metabolized drugs. The test is not informative for Crigler‑Najjar syndrome. Reduced UGT1A1 expression due to TA repeat variation and UGT1A1*6 variant elevates risk of adverse drug outcomes. Samples from individuals with recent transfusions or transplants may yield inaccurate results unless pre‑transplant DNA is used. Male liver or kidney dysfunction also independently affects drug response risk.