Els van de Vijver

29 Table 2 shows the diagnoses of patients without IBD. The majority of these patients did not need endoscopy to exclude IBD and had other tests including stool analyses for bacteria, ova and parasites, gastroscopy, abdominal ultrasound, CT-scan, Meckel scan, serology and dietary measurements leading to the diagnosis. Thirty-two children and teenagers were diagnosed with functional abdominal pain and were followed for at least 6 months to confirm this diagnosis. Seven of these patients had elevated calprotectin (range 97-400 µg/g stool) and 11 underwent endoscopy (including ileocolonoscopy) with negative results. Sixteen patients without IBD had abdominal ultrasound, six CT-enteroclysis and three abdominal MRI as part of their diagnostic work up. Seven patients had no definite diagnosis despite several tests and had spontaneous recovery of their ailments during follow up. Median time between faecal sampling for calprotectin and endoscopy was 22 days (range 0- 79) in the confirmed IBD-group and 42 days (0-164) in the non-IBD group (p=0.105). Diagnostic accuracy The pre-test probability of IBD in our study population was 36%. Calprotectin (cut-off point 50 μg/g) was elevated in all children and teenagers with IBD (sensitivity 100%, 95% CI 92% to 100%), and in 20 out of 75 patients without IBD (specificity 73%, 95% CI 62% to 83 %). Table 3 shows that a value above the cut-off point (in the absence of gastrointestinal infection) gives a specificity of 81% (95% CI 69% to 90%). Ruling out IBD without referral for endoscopy