Comparison of fecal calprotectin and serum C-reactive protein in early prediction of outcome to infliximab induction therapy

Background: Fecal calprotectin (FC) and serum C-reactive protein (CRP) are biomarkers of disease activity in Crohn's disease (CD) and ulcerative colitis (UC). We assessed FC, CRP, Harvey-Bradshaw index (HBi), partial Mayo Clinic Scoring (pMCS) and a cytokine panel during infliximab induction to predict therapy outcome. Methods: FC, CRP and clinical indices were evaluated in 123 (76 CD, 47 UC) patients before infliximab induction and after 12 weeks. Responders were monitored 48 weeks for an 'incident' (dosage increase, shortened dosage interval, surgery). Cutoff values for FC and CRP were obtained using receiver-operating characteristics (ROC). Disease progression was analyzed with Kaplan-Meier survivals, log-rank test and logistic regression for combined biomarkers. Cytokines were analyzed with Luminex multiplexing system. Results: Following infliximab, FC and CRP declined (p < .0001) along with HBi for CD and pMCS for UC. Simultaneously, IL-6 and TNF-alpha decreased, while IL-10 increased. Optimal FC ROC cutoff was 221 mu g/g (sensitivity 66%, specificity 67%, AUC 0.71) and CRP ROC cutoff 2.1 mg/L (sensitivity 54%, specificity 60%, AUC 0.58). In CD, FC > 221 mu g/g (p < .0001), but not CRP > 2.1 mg/L predicted an 'incident'. However, combined FC and CRP also predicted an 'incident' (p < .042). In UC, both FC > 221 mu g/g (p < .0005) and CRP > 2.1 mg/L (p = .0334) predicted 'incident', as did combined biomarkers (p < .005). Conclusions: Clinical disease activity is reduced by treatment with infliximab. In CD, persistently high FC, but not CRP, predict a treatment 'incident', whereas in UC both high FC and high CRP predict 'incident'. Combined FC and CRP values also predict an 'incident'.