Abstract
We recently published results of a community-based study in which unselected men and women aged 58 or 59 years, living in the ethnically mixed London boroughs of Brent and Harrow, were invited to have flexible sigmoidoscopy (FS) screening performed by a nurse. 1 Uptake rates were around 45%, which we noted was similar to uptake of the guaiac faecal occult blood test (gFOBT) used in the English Bowel Cancer Screening Programme (BCSP) in the same areas of London. Van Rossum 2 questions the validity of our comparison of uptake rates since the data were not acquired through a randomized trial. We acknowledge that a head-to-head comparison in a trial would be the ideal design, but uptake in the population is a key indicator for policy makers and has long been used to compare methods of delivery, time periods, or countries. We therefore believe that this comparison has value. In terms of identifying barriers to participation in colorectal cancer screening, the finding of similar uptake rates for two very different tests is important because it suggests that the key barriers to uptake lie less in the specific characteristics of either test than in the communalities.
We compared FS uptake rates with uptake of gFOBT rather than the immunochemical FOBT (iFOBT), since this is the test that is currently used in the BCSP. The relative merits of gFOBT and iFOBT are a different issue, but it is worth noting that van Rossum's study in the Netherlands shows that to achieve high sensitivity with iFOBT, positivity rates need to be relatively high: 5.5% at each screening round compared with 2.4% with gFOBT, 3 and the cumulative requirement for colonoscopy with biennial testing would be substantial. However, the BCSP plans to undertake a pilot to assess the feasibility of replacing gFOBT with iFOBT.
Van Rossum also objects to the use of a ‘once-only’ screening test. A single FS at age 55-64 years offers long-term protection because precancerous adenomas are detected and removed at an early stage and there is a long lead time for progression of new adenomas to cancers, hence continual ‘case-finding’ might not be justified. 4