Optimal cut-off value of fecal calprotectin for the evaluation of ulcerative colitis: An unsolved issue?

There is variability in the fecal calprotectin (FCP) cut-off level for the prediction of ulcerative colitis (UC) disease activity and differentiation from irritable bowel disease (IBS-D). The FCP cut-off levels vary from country to country.

We aimed to assess FCP as a marker of disease activity in patients with UC. We determined the optimal FCP cut-off value for differentiating UC and IBS-D.

In a prospective study, we enrolled 76 UC and 30 IBS-D patients. We studied the correlation of FCP with disease activity/extent as well as its role in differentiating UC from IBS-D. We also reviewed literature regarding the optimal FCP cut-off level for the prediction of disease activity and differentiation from IBS-D patients.

Sensitivity, specificity, positive predictive value, and negative predictive value of FCP (cut-off level, 158 μg/g) for the prediction of complete mucosal healing (using Mayo endoscopic subscore) were 90, 85, 94.7, and 73.3%, respectively. Sensitivity, specificity, positive predictive value, and negative predictive value of FCP (cut-off level, 425 μg/g) for the prediction of inactive disease (Mayo Score ≤ 2) were 94.3, 88.7, 86.2, and 95.4%, respectively. We also found a FCP cut-off value of 188 μg/g for the differentiation of UC from IBS-D.

The study reveals the large quantitative differences in FCP cut-off levels in different study populations. This study demonstrates a wide variation in FCP cut-off levels in the initial diagnosis of UC as well as in follow-up post-treatment. Therefore, this test requires validation of the available test kits and finding of appropriate cut-off levels for different study populations.