Correlation of Two Capsule Endoscopy Scoring Systems with Fecal Calprotectin: Does It Really Matter?

In the absence of a gold standard test, the diagnosis of isolated small bowel Crohn’s disease (CD) is often challenging. Clinical symptoms and signs are often nonspecific and may not correlate well with disease activity. We now know that barium small bowel imaging has limited value in evaluating mucosal lesions. Newer imaging modalities such as computed tomographic enterography (CTE) and magnetic resonance enterography (MRE) have higher sensitivity for detecting transmural inflammation [1], but they have limited value in evaluating isolated mucosal inflammation. Capsule endoscopy (CE), on the other hand, is an excellent, relatively non-invasive modality for direct mucosal visualization and thus can detect more subtle inflammatory change. As a result, CE is a useful tool for evaluating ulcerating diseases of the small bowel and may potentially aid in assessing disease activity and extent, as well as monitoring mucosal healing [2, 3]. However, one of the limitations has been the lack of an accurate and reproducible standardized scoring system that objectively assesses the severity of small bowel inflammation. In 2008, Gal et al. [4] published a simple, validated Capsule Endoscopy Crohn’s Disease Activity Index (CECDAI). This scoring index evaluates three parameters of small bowel pathology in CD: inflammation, extent of disease and presence of a stricture. All three parameters are calculated separately for the proximal and distal segments of the small bowel. This index has a high overall correlation (range 0.8–0.93; p \ 0.001) and agreement (0.867). Later, Gralnek et al. [5] developed the Lewis score (LS), which is based on villous edema, ulceration and stenosis detected on CE. An excellent inter-observer agreement for the global assessment of mucosal disease severity (84–86%) was noted, although the LS has not been prospectively validated. Both of these scoring indices potentially can be used for objectively measuring the degree of inflammatory activity. They may also be of benefit in assessing the degree of mucosal healing, which appears to be an important goal in the management of CD. Though these scoring indices are a step forward, there are important limitations. These indices were developed initially to standardize capsule reporting, but their use as a clinical tool is not yet clear and more prospective validation studies are needed. Simply stated, we do not know how accurately they measure the degree of mucosal inflammation. In addition, they have no discriminatory ability in differentiating CD from NSAID enteropathy, celiac disease, and/or ischemia. Other non-invasive methods have been studied to assess and quantify small bowel inflammation. One promising method is measurement of fecal calprotectin (FC). FC is a human protein, released into feces from activated granulocytes and inflamed epithelia [6]. The amount of FC in feces is proportional to the granulocyte migration to the gastrointestinal mucosa. Unlike the CE scoring indices, several studies have shown an excellent correlation of FC with the severity of mucosal inflammation [7, 8]. There are many studies that confirm that FC can differentiate inflammatory from non-inflammatory gastrointestinal disorders, including small bowel inflammation [8, 9]. Therefore, many consider FC a ‘‘gold standard,’’ reliable and highly specific marker of inflammation. So one might wonder if there is a correlation between FC and the current CE scoring indices and how it matters in measuring inflammation. S. R. Gurudu (&) J. A. Leighton Division of Gastroenterology and Hepatology, Mayo Clinic Arizona, 13400 East Shea Blvd, Scottsdale, AZ 85259, USA e-mail: Gurudu.Suryakanth@mayo.edu