Commonly used biomarkers do not contribute to diagnosing irritable bowel syndrome.

Objective: The aim of this article was to examine the costs and effectiveness of standardized blood and fecal investigations in patients fulfilling the Rome criteria for irritable bowel syndrome (IBS).

Methods: We conducted a real-life cohort study in patients fulfilling the Rome III criteria for IBS without red flag signs or symptoms, in a center of excellence for IBS patients from 1 January 2015 till 1 January 2019. Standardized blood and fecal investigations [hemoglobin (Hb), thyroid-stimulating hormone (TSH), coeliac serology, and fecal calprotectin (FCP)] were performed during the first consultation. Patients were followed for at least 1 year. Primary outcome was the probability of another diagnosis than IBS with subsequent overall costs.

Results: A total of 218 patients were included. In approximately 200 patients blood and fecal investigations were performed and 47 patients underwent a colonoscopy. Two-hundred ten patients were diagnosed with IBS, 5 with inflammatory bowel disease (IBD), 1 with nonspecific acute ileitis, 1 with hyperthyroidism, and 1 with coeliac disease. The number needed to diagnose all included laboratory tests was 34, and for the individual test: TSH 197, coeliac serology 199, and FCP 50. The total costs were approximately €4900 to diagnose one patient with another diagnosis than IBS.

Conclusion: In our real-life cohort of adult patients under the age of 50 years fulfilling the Rome criteria for IBS without red flag symptoms, standardized blood, and fecal investigations have a very low diagnostic yield accompanied by high additional costs. Colonoscopy is not indicated in patients with Rome III positive IBS and normal FCP.