Early proactive monitoring of DNA-thioguanine in patients with Crohn’s disease predicts thiopurine-induced late leucopenia in NUDT15/TPMT normal metabolizers

Figure 1 Flow chart of patient enrolment, exclusion, and follow-up. Late leucopenia was defined as a leukocyte count < 3.5 × 10⁹/L over two months. The stable dose (2.0 mg/kg/d azathioprine and 1.0 mg/kg/d 6-mercaptopurine, approximately) is reached approximately one to two weeks after the initial administration. NUDT15: Nudix hydrolase 15; TPMT: Thiopurine methyltransferase; 6TGN: 6-thioguanine nucleotides; DNATG: DNA-thioguanine.