For symptomatic patients, a concentration of ≥10 μg Hb/g faeces is considered a ‘positive’ result.10 These patients qualify for an urgent suspected cancer referral (previously called the ‘2-week-wait’ pathway) for investigation of their symptoms, primarily by colonoscopy, or computed tomography colonography (CTC) in those for whom a colonoscopy is inappropriate.6 This evidence concerns the gene GSTM1 and cancer.