Els van de Vijver

118 reassured that in patients with a low CRP (≤10 mg/L), normal haemoglobin and low FC (<250 µg/g), endoscopy can safely be avoided without missing a case of IBD. Effective therapeutic interventions in children with a negligible risk for IBD, e.g. gut-directed hypnotherapy, can be initiated without losing time on further diagnostics. Simultaneously, children with increased FC in combination with increased CRP, low haemoglobin, or both, who have a high risk for IBD, can have an endoscopic confirmation of this diagnosis sooner and consequently have an earlier start of appropriate treatment. Omitting the diagnostic strategy that comprises the combination of CRP, haemoglobin and calprotectin in children with non-bloody diarrhoea and abdominal pain may cause considerable harm, such as linear growth impairment(2) and progressive bowel damage requiring surgery early after diagnosis . (3-5) Tips for reliable faecal calprotectin results The reliability of the diagnostic strategy strongly depends on biological, pre−analytical and analytical factors influencing the FC test. Stool samples are relatively easy to obtain, but there are several obstacles in the trajectory from stool collection to analysis that can affect the test result. First, it is advisable to use the first bowel movement of the day to catch the highest possible concentration of calprotectin.(6) The faeces sample must not come into contact with toilet water as it may contain bleaches and disinfectants that may degrade calprotectin. Secondly, medication that is commonly prescribed in patients with abdominal pain, including non-steroidal anti-inflammatory drugs (e.g. aspirin or ibuprofen) and proton pump inhibitors, can increase FC.(7, 8) Ideally, these medications should be discontinued a week before stool collection. Thirdly, recent publications have shown that the protein calprotectin may be less stable at room temperature than previously thought.(6, 9, 10) Protein degradation can be delayed when the filled stool container is refrigerated until delivery at the laboratory. Unrefrigerated stool samples of children with vague gastrointestinal complaints that arrive with a delay exceeding 48 hours and with a FC result between 50 and 250 μg/g, may falsely reassure doctors and patients because of degradation of initially increased FC levels and therefore require analysis of another fresh faecal sample. Chapter 7 118