Low 6-thioguanine nucleotide level: Effective in maintaining remission in Chinese patients with Crohn's disease

Background and Aim: Measuring 6-thioguanine nucleotide (6-TGN) level is useful in optimizing dose of azathioprine (AZA) and monitoring for toxicity. Lower dose of AZA was suggested for maintenance of clinical remission in Asian patients than Caucasian patients with Crohn's disease (CD). However, the optimal 6-TGN threshold required in Asian patients is undetermined. Therefore, the aim of the current study is to explore the optimal 6-TGN threshold required in Asian patients with CD for maintenance of clinical remission. Methods: A retrospective cohort study in a tertiary referral center recruited 252 CD patients. The primary endpoint was disease relapse. The levels of 6-TGN and AZA dose were compared in remission group and relapse group. Remission rate was compared across the increased 6-TGN level and dose range. Results: Patients with 6-TGN range of 0–180.94 pmol/8 × 10 ⁸ red blood cells (RBC) had lower remission rate compared with those with 180.94–255.50 pmol/8 × 10 ⁸ RBC (P = 0.020). Quartile analysis showed that increasing 6-TGN level beyond 180 pmol/8 × 10 ⁸ RBC produced negligible gain in rate of remission. Frequency of adverse events significantly increased in patients with 6-TGN level > 355 pmol/8 × 10 ⁸ RBC (8.0% with 6-TGN > 355 pmol/8 × 10 ⁸ RBC vs 2.7% with 6-TGN < 355 pmol/8 × 10 ⁸ RBC, P = 0.035). Conclusion: Our study suggested that optimal 6-TGN threshold required to maintain clinical remission in Chinese patients was 180–355 pmol/8 × 10 ⁸ RBC.