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 µg/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 µg/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 µg/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 µg/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.
Keywords: Crohn’s disease; Crohn’s disease activity index; fecal calprotectin; inflammatory bowel diseases.