Els van de Vijver

33 about the use of these drugs in the study population, which could be the reason why some children with functional abdominal pain had elevated faecal calprotectin. In a cross-sectional study of school-aged children with functional abdominal pain and irritable bowel syndrome, slightly elevated calprotectin concentrations were found in their stools compared with control children.(12) However, the concentrations were clearly in the lower range (65+/- 75 μg/g) while the majority of confirmed IBD cases in our population had concentrations way above 500 μg/g on their first presentation. Applicability of findings to paediatric care Pre-test probability of IBD in our study population was 36%. The study population was a combination of patients from secondary and tertiary care hospitals, where the emphasis is usually on “ruling in”: increasing the probability of IBD before carrying out more expensive, time-consuming and invasive procedures; establishing a firm diagnosis; and starting appropriate treatment. A diagnostic test with a high specificity is therefore preferred.(13) In this study we tested the “ruling out” properties of faecal calprotectin in paediatric practice. We found that a normal calprotectin level reduces the probability of IBD to zero. In other words, the diagnosis IBD can be ruled out with confidence. The paediatrician does not need to refer the patient for endoscopic evaluation, but instead can provide reassurance or adopt a “ watchful waiting” strategy. C-reactive protein (CRP) is a far less reliable test to rule out IBD than calprotectin. In a recently published paper a large number of children and teenagers with newly diagnosed IBD proved to have normal CRP levels.(14) The conclusions of this study cannot simply be translated into the practice of the general practitioner or family doctor. IBD prevalence in the general population is much lower. In the first-line setting the number of false-positive calprotectin results will therefore increase, exposing too many patients without IBD to unnecessary endoscopic procedures. At present, there is no evidence of how the test performs in primary care. If studies conducted in primary care find a high diagnostic accuracy of the faecal calprotectin test it, will be an important step forward in how IBD is diagnosed. Ruling out IBD without referral for endoscopy