GSTM1 and anemia (phenotype): stratified patients presenting in primary care with any lower GI symptoms (except rectal bleeding or a rectal mass) by f-Hb level, and anaemia in one strata.23 PPVs were: 30.0% in the ≥150.0 μg Hb/g faeces group; 4.4% in the 10.0–149.9 μg Hb/g faeces group; 0 in the 4.0–9.9 μg Hb/g faeces with anaemia group, 2.9% in the 4.0–9.9 μg Hb/g faeces without anaemia group and 0.2% in the <4.0 μg Hb/g faeces group.