Endoscopic Factors Influencing Fecal Calprotectin Value in Crohn's Disease

Fecal calprotectin [fcal] is a biomarker of Crohn's disease [CD] endoscopic activity. Identifying the endoscopic situations in which fcal is less reliable remains unexplored. We aimed to determine the endoscopic factors influencing fcal level in CD.

Overall, 53 CD patients consecutively and prospectively underwent colonoscopy, with CD Endoscopic Index of Severity [CDEIS] calculation and stool collection. Fcal was measured using a quantitative immunochromatographic test. Correlation analysis was done with Pearson statistics.

Fcal was correlated with CDEIS [0.66, p < 0.001]. In univariate analysis, fcal was correlated with the affected surface [0.65, p < 0.001] and the ulcerated surface [0.47, p < 0.001]. Fcal was significantly associated with ulceration depth, with median fcal of 867.5 µg/g, 1251.0 µg/g, and 1800.0 µg/g, in patients presenting with non-ulcerated lesions, superficial ulcerations [SU], and deep ulcerations [DU], respectively. Lesion locations did not influence fcal. In multivariate analysis, fcal was associated with affected surface [p = 0.04] and the presence of CD lesions. Moreover, fcal increased with the ulceration depth [p = 0.03]. However, ulcerated surface and CD location did not affect fcal. Using a receiver operating characteristic [ROC] curve, we showed that fcal of 400 µg/g was the best compromise between sensitivity [0.76] and specificity [0.77], whereas fcal ≥ 200 µg/g was highly sensitive [0.86] to detect SU or DU.

Fcal is a very reliable biomarker to detect endoscopic ulcerations in CD. We suggest repeating measurement in case of intermediary results [200-400 µg/g] in daily practice. Fcal level is mostly influenced by the presence of CD lesions [even non-ulcerated], in a depth-related manner and by the affected surface.