Introduction Diagnosis of inflammatory bowel disease (IBD) in primary healthcare is challenging and often associated with a considerable diagnostic delay. This delay is associated with worse disease progression and outcomes. Although testing for faecal calprotectin is a useful screening tool to identify patients who need endoscopy for IBD, the widespread use may not be appropriate due to the low prevalence of patients with IBD among all patients attending a general practitioner (GP) with gastrointestinal symptoms. To increase the appropriate application of the faecal calprotectin test, an 8-item questionnaire, the CalproQuest, has been developed to increase pretest probability for a positive test result.

Methods and analysis This is a prospective diagnostic trial. The study consists of two independent and consecutive parts A and B, conducted by gastroenterologists (A) and GPs (B), respectively. Patients included in part A are referred to the gastroenterologist for any endoscopic evaluation. Patients included in part B present at their GP because of ongoing unspecific gastrointestinal symptoms (abdominal pain, bloating, stool irregularities, diarrhoea) for at least 2 weeks. CalproQuest consists of four main and four secondary questions specific for IBD; it is considered positive if ≥2 main criteria are answered positively or one main criterion and two secondary criteria are answered positively. In part A, the sensitivity and specificity of CalproQuest for stool calprotectin levels ≥50 μg/g faeces and for positive IBD diagnosis will be investigated. In part B, the feasibility of CalproQuest in daily primary healthcare practice will be assessed.

Ethics and dissemination The study protocol was approved by the Ethics Committee of the Kanton Zurich (reference KEK-ZH-number 2013-0516). The results will be published in a peer-reviewed journal and shared with the worldwide medical community.

Trial registration number ISRCTN66310845.