The current guidelines recommend that patients can be diagnosed with IBS, in the absence of ‘red flags’, when: their symptoms fulfil the Rome IV criteria for IBS; their full blood count, coeliac serology, C reactive protein and erythrocyte sedimentation rate are normal; and they have a faecal calprotectin level of < 50 μg/g11,12. The gene discussed is CRP; the disease is irritable bowel syndrome.