Many patients with Crohn's disease who achieve pharmacologically induced remission experience relapse within 12 months. Factors that are predictive of relapse have been identified but specific data on biologic variables that predict short-term relapse are lacking.OBJECTIVE
To identify biologic variables that predict short-term relapse in patients with Crohn's disease.DESIGN AND INTERVENTION
This study included patients with Crohn's disease who had achieved clinically induced remission in a previous, randomized, controlled, therapeutic trial. Patients in the trial were followed up every 6 weeks for 12 months or until withdrawal from the trial or relapse. Biomarkers, including full blood counts, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), were measured at each follow-up visit. Exclusion criteria included lack of follow-up data or lack of evaluation of biomarkers. A relapse of disease was defined as the need for surgery or an increase in Crohn's Disease Activity Index (CDAI) of ≥100 points compared to the CDAI score at remission. Data were analyzed to identify biomarkers that predicted relapse of Crohn's disease, and a binary biologic predictive score was developed from this information. The sensitivity and specificity of the score determined and an assumed relapse rate of 10% for every 6 weeks of follow-up was used to calculate negative and positive predictive values.OUTCOME MEASURES
The main outcome measure was identification of biologic variables that predicted short-term relapse.RESULTS
In total, 71 patients (mean age 25 years, range 21-34 years) were included in the study, 38 of whom experienced clinical relapse of disease. Multivariate analysis revealed that CRP >20 mg/l, ESR >15 min and the combination of CRP >20 mg/l and ESR >15 min were significantly associated with an increased risk of relapse: relative risk (RR) 10.5 (95% CI 2.3-48.1), 6.1 (95% CI 1.9-18.9) and 9.9 (95% CI 3.3-29.7), respectively (P<0.001 for all associations). The binary biologic predictive score that was developed was positive if CRP was >20 mg/l and ESR was >15 min and negative if both variables were below, or at these limits. The RR of short-term relapse in patients with a positive biologic predictive score was 8.0 (95% CI 2.8-22.9). The sensitivity and specificity of the score were 89% (95% CI 74-94%) and 43% (95% CI 37-49%), respectively, in diagnosing short-term relapse. Assuming a 10% relapse rate every 6 weeks, the negative and positive predictive values of the score were 97% and 15%, respectively.CONCLUSION
The biologic predictive score calculated from CRP levels and ESR can predict short-term relapse effectively in patients with Crohn's disease in clinical remission.