Colorectal cancer screening programme: is the French faecal immunological test (FIT) threshold optimal?

BACKGROUND

In France, the colorectal cancer organised screening programme uses the faecal immunological test. A positive test ⩾30 μg Hb/g of stool leads to a colonoscopy for identification of potential colorectal lesions. Cut-off values vary from 20 to 47 μg Hb/g of stool in Western countries. We herein question this threshold's relevance in a French population and perform a retrospective observational study using the Parisian database between 1 April 2015 and 31 December 2018.

METHODS

Rates of participation, numbers of positive faecal immunological test (FIT), detection rates and positive predictive values for advanced adenomas and/or colorectal cancer were determined. Mean positivity values for colorectal lesions were calculated.

RESULTS

In our population, there were 4.1% positive tests and 67.6% colonoscopy results available with final reports. Positive predictive value for advanced adenomas and colorectal cancer were 30% [95% confidence interval (CI) 29.8-30.3] and 7.4% (95% CI 7.35-7.52), respectively. The mean positivity value for all positive tests in our population was 101.7 µg Hb/g of stool (95% CI 85-118.3). There were 1136 normal colonoscopies (21.4%) with a mean positivity value of 88.6 μg Hb/g of stool. Following a negative test in a first screening campaign, 40.8% of patients in our population performed a second test with a positivity rate of 1.3% and with the encounter of 81 colorectal cancers. The risk of having a positive test during the second screening campaign and finding advanced colorectal lesions significantly increased (all p < 0.001) when comparing negative FIT results ranging between 15 and 29 μg Hb/g of stool to 0 and 14 μg Hb/g of stool from the previous campaign.

CONCLUSION

Using the current positivity threshold, some patients were considered negative with a delay in colorectal cancer diagnosis, suggesting the threshold could be lowered. Also, the mean positivity value for normal colonoscopies was high, raising the question of upper gastrointestinal bleeding.

A systematic review of the psychological impact of false-positive colorectal cancer screening: What is the role of the general practitioner?

Screening for colorectal cancer (CRC) has both advantages (e.g. reduction in morbidity and mortality) and disadvantages (e.g. false positives and distress). A systematic review was therefore performed to improve our understanding of how false-positive CRC screening results affect patients psychologically (and to make recommendations for primary care). The PubMed, Embase, PsychINFO, CINAHL and Cochrane databases were searched in October 2014 and supplemented in December 2016 to identify studies on the psychological impact of false-positive CRC screening. Original studies were eligible when they assessed psychological impact in a screening setting, provided they also included false-positive CRC screening results. Two authors independently assessed 2,367 available manuscripts and included seven. Heterogeneity in their outcome measures meant that data could not be pooled. Two studies showed that a false-positive CRC screening result caused some moderate psychological distress shortly before and after colonoscopy. The remaining five studies illustrated that the psychological distress of patients with true-positive and false-positive CRC screening results was comparable. We conclude that a false-positive CRC screening result may cause some moderate psychological distress, especially just before or after colonoscopy. We recommend that general practitioners mention this when discussing CRC screening with patients and monitor those with a false-positive outcome for psychological distress.