Is there any utility in checking HLA-B*5801 in our Black and Asian patients who are already tolerating allopurinol?

I don't believe there is any value in checking HLA0B*5801 once the patient has been on allopurinol therapy for several weeks or months as allergic reactions, particularly SJS and TENS, occur within the first few weeks of treatment. Further, a positive test, weeks to months after beginning allopurino...