Background: The clinical pictures of functional gastrointestinal disorders and inflammatory diseases can be quite similar leading to inappropriate and expensive investigations. Objective. To investigate fecal calprotectin (FC) diagnostic performance in different gastrointestinal conditions.
Material and methods: Stool specimens of 66 outpatients referred for colonoscopy were collected for further FC determination. Diagnostic accuracy was assessed by the area under the curve (AUC). Sensitivity (Se), specificity (Sp), positive (PPV), and negative predictive values (NPV) were calculated according to the presence of inflammation and the main final diagnosis.
Results: Histological inflammation was found in 45 (68%) patients: 24 had a diagnosis of inflammatory bowel disease (IBD) while 21 reported miscellaneous conditions (5 microscopic colitis, 2 eosinophilic colitis, and 14 nonspecific chronic colitis). The diagnosis in the 21 (32%) patients without inflammation was irritable bowel syndrome (IBS). Median FC values were 268 µg/g (95% CI, 151-343) and 49 µg/g (95% CI, 23-101) in patients with and without inflammation, respectively (p = 0.0001). AUC value of FC was 0.811 (Se = 68.9%, Sp = 71.4%, PPV = 83.8%, and NPV = 56.3% with a cutoff value of 100 µg/g) for discriminating between patients with and without inflammation and 0.931 (Se = 87.5%, Sp = 90.5%, PPV = 91.3%, and NPV = 86.4% with a cutoff value of 150 µg/g) for discriminating between patients with IBS and IBD. Using the cutoff value recommended by the manufacturer (50 µg/g), we found Se =100%, Sp =52.4%, PPV =70.6%, and NPV =100% for the diagnosis of IBD.
Conclusions: FC appears to be a reliable noninvasive biomarker of intestinal inflammation useful to improve the appropriateness of colonoscopy requests.
Keywords: fecal calprotectin; inflammatory bowel disease-clinical; irritable bowel syndrome.