Noninvasive Monitoring After Azathioprine Withdrawal in Patients With Inflammatory Bowel Disease in Deep Remission

Background & Aims: There is uncertainty regarding the optimal duration of treatment with azathioprine (AZA) in ulcerative colitis (UC) and Crohn's disease (CD). We analyzed the clinical course and predictors of relapse after AZA withdrawal in patients in sustained deep remission. Methods: A prospective study was performed on patients who stopped their treatment with AZA while being in steroid-free, extended deep remission (normal clinical, endoscopic, and histologic indexes, C-reactive protein, and fecal calprotectin [FC]). Standard biochemical tests and FC were measured at 3 and 6 months, then every 6 months. Bowel ultrasounds and ileocolonoscopy were performed every 6 and 12 months, respectively. Multivariate analysis for predictors of relapse was performed using a Cox proportional hazards model and hazard ratios were calculated. Spearman nonparametric correlation test was also used. The accuracy of significant predictors was calculated. Results: Fifty-seven patients with inflammatory bowel disease stopped AZA after median 7 years (range, 5–19) and were followed up for median 50 months (range, 25–85). Twenty-six patients (18/31 UC, 8/26 CD; P = .003) relapsed, within a median 15 months (range, 2–37). FC was the only variable significantly correlated with later relapse of both diseases (UC: hazard ratio, 3.3; 95% confidence interval, 1.2–10; CD: hazard ratio, 4.5; 95% confidence interval, 1.4–12.5). The sensitivity, specificity, and positive and negative predictive values of FC were 50%, 100%, 100%, and 59% in UC and 50%, 94%, 80%, and 81% in CD. Conclusions: More than half patients with UC and one-third of patients with CD relapse after AZA withdrawal despite previous deep remission. FC positivity is associated with high risk of relapse, allowing early correction of the therapeutic strategy.