Measuring Erythrocyte Thiopurine Methyltransferase Activity in Children-Is It Helpful?

Objective: To assess the profile of thiopurine transmethyltransferase (TPMT) enzyme activities in children and discuss the utility of measuring TPMT levels before commencing azathioprine therapy.

Study Design: Retrospective study in a single pediatric center of all patients who had TPMT enzyme assay measured during a 3-year period before the start of azathioprine therapy. Patients' TPMT enzyme activities were classified as normal (26-50 pmol/h/mgHb), intermediate (10-25 pmol/h/mgHb), and deficient (<10 pmol/h/mgHb).