Much current interest exists in using very low faecal haemoglobin concentrations (f-Hb) in many clinical settings, including CRC screening,6 assessment of patients presenting with lower gastrointestinal symptoms7 and in adenoma surveillance programmes.8 One rationale is that the lower the f-Hb threshold applied to guide further investigation, the more neoplasia will be detected. The gene discussed is GSTM1; the disease is colorectal carcinoma.