GSTM1 and adenoma: suggest that this tendency may be a marker of systemic inflammation.10 Others have found that older participants have more false positive FIT results at the low threshold of 17 μg/g.11 In our data, with a threshold of 20 μg/g, there is also some evidence of this, with proportions of complete cases having no CRC or adenoma but with f-Hb of 20 μg/g or more being 2.8%, 3.1% and 3.3% for age groups 59–64, 65–69 and 70–75 years respectively (p = 0.045).