Els van de Vijver

65 Table 1: Overview of predictors Test Measurement Definition of positive result Symptoms Persistent non-bloody diarrhoea History Duration ≥4 weeks Recurrent non-bloody diarrhoea and abdominal pain History ≥2 episodes in 6 months Unintended weight loss History and physical examination > 1 kg First degree relative with IBD History Affected father, mother, sibling Extra-intestinal symptoms Physical examination Episcleritis, uveitis, erythema nodosum, psoriasis, finger clubbing, arthritis Blood markers Increased C-reactive protein Local laboratory >10 mg/L Anaemia (haemoglobin <−2 SD for age and gender) Local laboratory 4-12 years < 7.1 mmol/l boys 12-18 years < 8.1 mmol/l girls 12-18 years < 7.4 mmol/l Stool markers Increased faecal calprotectin Central laboratory 1 ≥250  g/g 1 fCAL enzyme-linked immunosorbent assay, BÜHLMANN Laboratories AG, Schönenbuch, Switzerland We estimated the performance of the four diagnostic strategies by calculating (1) the area under the receiver-operating-characteristics curve (AUC), and (2) the net benefit of each strategy through decision curve analysis. Net benefit combines the number of children that were correctly triaged for endoscopy (true positives) and the number of children exposed to an unnecessary endoscopic procedure (false positives) into a single number. We show the net benefit of each strategy through a range of risk thresholds. Finally, we calculated sensitivity and specificity with 95% confidence intervals (CIs) of the optimal diagnostic strategy. Computations were carried out with R (version 3.5.1). Test strategies to predict IBD 65