GOALS

The aim of this study was to assess whether sustained 6-thioguaninenucleotide (6-TGN) levels were associated with improved long-term outcomes in patients with inflammatory bowel diseases (IBD).

BACKGROUND

Cross-sectional data have shown that thiopurine metabolites are correlated with clinical efficacy in patient receiving thiopurines for IBD but the role for serial measurements through treatment course is unclear.

STUDY

We conducted a retrospective cohort study including patients with IBD on thiopurine monotherapy and had serial 6-TGN levels measured. Predictive variables included demographics, disease phenotype, 6-TGN levels (nadir, median, and peak levels). The primary outcome was the development of a disease relapse. The secondary outcome was the need for IBD surgery.

RESULTS

Two hundred eighteen 6-TGN samples from 87 patients were analyzed. Nadir and median 6-TGN levels were significantly higher in patients who did not relapse [185 and 233 pmol per 8×10 red blood cells (RBCs)] as compared with levels in patients who did relapse (150 and 167 pmol per 8×10 RBCs, P=0.025) but there was no significant difference in peak 6-TGN level. When adjusted for confounding factors, a nadir 6-TGN level ≥161 and a median 6-TGN level ≥264 were associated with a significant decrease in the rate of disease exacerbation (hazard ratio: 0.5; 95% confidence interval, 0.26-0.87; P=0.016 and hazard ratio: 0.4; 95% confidence interval, 0.2-0.82; P=0.14).

CONCLUSIONS

Serial thiopurine metabolite level assessments and dose adjustment aiming to maintain higher 6-TGN levels may be helpful to improve long-term outcomes in patients with IBD.