Noninvasive Markers of Disease Activity in Inflammatory Bowel Disease.

It is often difficult to assess disease activity in inflammatory bowel disease (IBD). Noninvasive biomarkers are a means of quantifying often nebulous symptoms without subjecting patients to endoscopy or radiation. This paper highlights markers present in feces, serum, or urine that have all been compared with the gold standard, histologic analysis of endoscopically collected specimens. Two categories of markers are featured: well-researched markers of mucosal inflammation with high sensitivity and specificity (calprotectin, lactoferrin, and S100A12) and novel promising markers, some of which are already clinically employed for reasons unrelated to IBD (interleukin [IL]-17, IL-33/ST2, adenosine deaminase, polymorphonuclear elastase, matrix metalloproteinase-9, neopterin, serum M30, and fecal immunohistochemistry). The data pertaining to the more-established markers are intended to highlight recent clinical applications for these markers (ie, assessing disease outside of the colon or in the pediatric population as well as being a cost-saving alternative to colonoscopy to screen for IBD). As there is no evidence to date that a specific marker will accurately be able to represent the entire IBD patient population, it is likely that a combination of the existing markers will be most clinically relevant to the practicing gastroenterologist attempting to evaluate disease severity in a specific patient. Familiarity with the most promising emerging markers will allow a better understanding of new studies and their impact on patient care.