A significantly higher proportion of screenees with faecal Hb levels of 150–200 (47%) and ⩾200 (61%) had advanced neoplasia than screenees with faecal Hb levels of 50–150 ng (25%) (P=0.009 and P<0.001, respectively), whereas the proportions were similar among screenees with values of 50–100 ng ml−1 and 100–150 ng ml−1 (25 vs 18%; P=0.60). Here, GSTM1 is linked to neoplasm.