We read with interest Dr McCartney’s concerns over the provision of screening tests in the private sector[1]. In particular, the concern raised over the use of whole body CT with regards to the false positives that can be generated. Whilst not currently used in the NHS as a primary screening tool, abdominal CT is utilised as a diagnostic tool following a positive screening result. CT colonography is one of the options used within the Scottish Bowel Screening Programme for patients who, following a positive faecal occult blood test (FOBt), have incomplete colonoscopies or (rarely) in those who are unfit to proceed for initial colonoscopy. In addition to imaging the large bowel, this procedure also images the abdominal viscera and lung bases.

In the first complete round of screening in NHS Greater Glasgow & Clyde, 106 patients underwent CT colonography of which 20 (19%) patients had significant incidental extra-colonic findings that required further investigation. This ranged from the relatively minor, such as a dilated common bile duct that required LFTs to be checked, to the major, such as a lesion that required a CT guided biopsy and PET scan to fully assess. Clearly these findings can have both a physical and psychological impact on the otherwise asymptomatic patient. Whilst currently these represent a relatively small number of those who participate in screening (over 4 500 people attended for screening colonoscopy in the first round in NHS GG&C), with the expected introduction of immunochemical faecal tests (FIT) the positivity rate is expected to increase [2]. It is likely that the number of colonoscopies performed and as a result the number of incomplete colonoscopies will increase and this may have a knock on effect on the number of CT pneumocolons that are performed. It is important to highlight that before proceeding on to CT colonography in these screened patients, informed consent must be properly sought with particular reference to the implications of detecting extra-colonic pathology.

1. McCartney M. What companies don't tell you about screening. BMJ 2012;344:e2311.
2. van Rossum LG, van Rijn AF, Laheij RJ, van Oijen MG, Fockens P, van Krieken HH, et al. Random comparison of guaiac and immunochemical fecal occult blood tests for colorectal cancer in a screening population. Gastroenterology 2008;135(1):82-90.

Competing interests: None declared