Diagnostic Accuracy of Fecal Calprotectin Concentration in Evaluating Therapeutic Outcomes of Patients With Ulcerative Colitis

BACKGROUND & AIMS: Histologic features of inflammation (histologic inflammation) are associated with clinical relapse in patients with ulcerative colitis (UC). Concentration of fecal calprotectin (FC) can be used to identify patients with mucosal inflammation. We aimed to assess the accuracy of FC measurements in identifying patients with histologic inflammation and to develop a model to predict outcomes of therapy. METHODS: We performed a post hoc analysis of data from a phase 4 trial of the efficacy of multimatrix mesalamine in patients with mild to moderate UC (the MOMENTUM trial). We obtained clinical, endoscopic, and histologic data from week 8 (n = 639) and week 52 (n = 373) of the trial. We used area under the receiver operating characteristic curves to determine the accuracy and optimal cut-off values of FC in identifying patients with different therapeutic outcomes (clinical remission, endoscopic healing, deep remission, or histologic remission) at week 8 and week 52. We performed multivariable logistic regression analyses to identify factors associated with these outcomes. RESULTS: Median FC concentrations were lower in patients who achieved outcomes of clinical remission, endoscopic healing, deep remission, or histologic remission vs patients who did not. FC concentrations identified patients with endoscopic healing and histologic remission with area under the receiver operating characteristic curve values of 0.77 and 0.76 at week 8, and 0.79 and 0.80 at week 52, respectively. The optimal FC cut-off concentrations for identification of patients with histologic remission were 75 mu g/g at week 8 and 99 mg/g at week 52. In the subpopulation with an endoscopy score of 0, median FC concentrations were lower in patients with histologic remission than in patients with microscopic inflammation at week 8 (30 vs 140 mu g/g; area under the receiver operating characteristic, 0.72) and week 52 (21.5 vs 134.5 mu g/g; area under the receiver operating characteristic, 0.71). At both time points, the optimal FC cutoff concentration was approximately 75 mu g/g. Our final prediction model for week 52 histologic remission comprised endoscopic score at week 8, FC concentration at week 8, and histologic activity at baseline and week 8. CONCLUSIONS: A post hoc analysis of data from a phase 4 trial found that, even in patients with complete endoscopic healing of UC, FC concentration can be used to discriminate patients with ongoing microscopic inflammation from patients with histologic remission. The optimal cut-off concentration of FC is between 75 and 100 mu g/g.