What is the evidence for fecal calprotectin thresholds to distinguish indeterminate colitis from CD, and how reliable are these cutoffs across laboratories

What is known

- Calprotectin correlates with endoscopic and histologic mucosal inflammation and is used to distinguish inflammatory from non-inflammatory GI conditions, not to subtype IBD. ^1–3 - Reported calprotectin sensitivity and specificity vary across studies depending on the chosen cutoff value. ^2,4 - Fecal markers differentiated IBD from other forms of colitis with only 43–50% overall accuracy. ⁵ - In one small pediatric series, indeterminate colitis cases had low calprotectin values, but the numbers were too few to define a distinguishing threshold. ³

What is unknown / caveats

- Excerpts address calprotectin for diagnosing IBD or detecting inflammation, not for separating IBD subtypes - Cutoff performance varies by threshold and assay, and one study could not compute an optimal cutoff because values above 500 were not diluted - Indeterminate-colitis data are limited to a few pediatric cases - No retrieved study evaluated a calprotectin cutoff specifically to separate indeterminate colitis from Crohn's disease, so reliability for that use cannot be assessed.

## References

1. Rosenfeld G, Greenup AJ, Round A, Takach O, Halparin L, Saadeddin A, Ho JK, Lee T, Enns R, Bressler B. FOCUS: Future of fecal calprotectin utility study in inflammatory bowel disease. World J Gastroenterol. 2016;22(36):8211-8. PMID: 27688663.

2. Ho SSC, Ross M, Keenan JI, Day AS. Fecal Calprotectin in Combination With Standard Blood Tests in the Diagnosis of Inflammatory Bowel Disease in Children. Front Pediatr. 2020;8:609279. PMID: 33748035.

3. Bunn SK, Bisset WM, Main MJ, Gray ES, Olson S, Golden BE. Fecal calprotectin: validation as a noninvasive measure of bowel inflammation in childhood inflammatory bowel disease. J Pediatr Gastroenterol Nutr. 2001;33(1):14-22. PMID: 11479402.

4. Pivac I, Jelicic Kadic A, Despot R, Zitko V, Tudor D, Runjic E, Markic J. Characteristics of the Inflammatory Bowel Disease in Children: A Croatian Single-Centre Retrospective Study. Children (Basel). 2023;10(10). PMID: 37892340.

5. Turkay C, Kasapoglu B. Noninvasive methods in evaluation of inflammatory bowel disease: where do we stand now? An update. Clinics (Sao Paulo). 2010;65(2):221-31. PMID: 20186307.

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_Draft, generated by the IBDology RAG and not yet clinician-reviewed. Answers are grounded in the retrieved literature listed above; a high faithfulness score means the answer matches its sources, not that the sources are correct._