GSTM1 and colorectal carcinoma: In patients with undetectable f-Hb, 617 patients would need to undergo colonoscopy to detect 1 CRC; hence clinical acumen and safety-netting remains essential to identify patients with CRC and false negative FIT.28 The ROC AUC of 0.93 (0.92–0.95) confirms that the diagnostic accuracy of FIT is excellent, and on its own is at least as good as risk scores such as FAST (AUC 0.91) or COLONPREDICT (AUC 0.92) that combine FIT with other patient characteristics such as demographics, serum Hb and symptoms.29 30