Can fecal calprotectin better stratify Crohn's disease activity index?

Background Crohn's disease (CD) activity index (CDAI) is still widely used for monitoring clinical activity in CD patients, but is of little value as indicator of persistent inflammation in symptomless patients. Fecal calprotectin levels >= 150 mu g/g are strongly indicative of endoscopically and/or histologically active disease. Our aim was to study, in a large cohort of CD patients, the relationship between CDAI and fecal calprotectin levels. Methods CDAI and fecal calprotectin levels were evaluated in consecutive patients from a CD outpatient clinic. Results We enrolled 193 CD patients, of whom 38% with CDAI <150 had a calprotectin value >= 150 mu g/g, suggestive of active disease. A logistic regression model showed that for CDAI levels between 100 and 150, the estimated logistic probability of calprotectin >= 150 mu g/g increased progressively to 76%, reaching 94% where disease activity was localized in the colon. With a CDAI cut-off >120, we found a high diagnostic accuracy of 72%, with 88% specificity and 50% sensitivity (positive predictive value: 76%, negative predictive value: 71%) to identify a calprotectin value >= 150 mu g/g. Conclusion CDAI scores between 100 and 150 display an acceptable ability to quantify the risk of persistent inflammation as expressed by the high calprotectin level.