GSTM1 and colorectal carcinoma: After one negative FIT, participants with f‐Hb just below the cut‐off (>40‐46.9 μg/g) had a higher probability of detecting an interval CRC (OR 16.9; 95%CI: 14.0‐20.4) than had participants with unmeasurable f‐Hb (0‐2.6 μg/g).