Fecal Calprotectin Intra-stool and Intra-individual Variability
Stool samples(fecal) are not homogenous when compared to blood samples. Inflammatory bowel disease risk cannot be determined depending on a single measurement as stool samples are not homogenous. Calprotectin, pancreatic elastase and lactoferrin markers vary in each bowel movement.
One study of fecal calprotectin found 17% variation within the same stool specimen depending upon the part of stool sampled in the specimen. The same study found 36% variation in fecal calprotectin with 2 stool samples taken a few days apart.
Every test has strengths, limitations, and scientific uncertainties, and requires clinical correlation with multiple diagnostic criteria and classifications. Few diseases have a single clinical, laboratory, pathological, or radiological feature that serves at the ‘gold standard’ in support of diagnosis or classification.
Fecal calprotectin at low grade inflammatory/non-pathological levels may respond more rapidly to anti-inflammatory approaches. Consider the following excerpt from the article from the Journal of Gastroenterology & Hepatology:
“Fecal calprotectin levels over 200 µg/mg have a higher positive predictive value for pathology, and values of 500 to 600 µg/mg nearly guarantee pathology findings. It is important to keep in mind that fecal calprotectin is inflammation- and not disease-specific. Almost every colonic disease and many small bowel diseases are associated with inflammation and, hence, test positive for calprotectin. However, most of these diseases are associated with low-grade inflammation, such as nonsteroidal anti-inflammatory drug (NSAID) enteropathy, although calprotectin values over 500 to 600 µg/mg are extremely predictive of IBD or food infections. However, there are no fixed rules for calprotectin values. As clinicians use the calprotectin test more often, they improve in judging the test results in relation to the symptoms of patients.”
References
Bjarnason I. (2017). The use of fecal calprotectin in inflammatory bowel disease. Gastroenterology & Hepatology, 13(1), 53–56. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390326/pdf/GH_13_53.pdf
Cremer, A., Ku, J., Amininejad, L., Bouvry, M. R., Brohet, F., Liefferinckx, C., Devière, J., van Gossum, A., Smet, J., Stordeur, P., & Franchimont, D. (2019). Variability of faecal calprotectin in inflammatory bowel disease patients: An observational case-control study. Journal of Crohn's & Colitis, 13(11), 1372–1379. Retrieved from: https://doi.org/10.1093/ecco-jcc/jjz069