A national cluster-randomised controlled trial to examine the effect of enhanced reminders on the socioeconomic gradient in uptake in bowel cancer screening

Background: The NHS Bowel Cancer Screening Programme in England offers biennial guaiac faecal occult blood testing (gFOBt). There is a socioeconomic gradient in participation and socioeconomically disadvantaged groups have worse colorectal cancer survival than more advantaged groups. We compared the effectiveness and cost of an enhanced reminder letter with the usual reminder letter on overall uptake of gFOBt and the socioeconomic gradient in uptake. Methods: We enhanced the usual reminder by including a heading 'A reminder to you' and a short paragraph restating the offer of screening in simple language. We undertook a cluster-randomised trial of all 168 480 individuals who were due to receive a reminder over 20 days in 2013. Randomisation was based on the day of invitation. Blinding of individuals was not possible, but the possibility of bias was minimal owing to the lack of direct contact with participants. The enhanced reminder was sent to 78 067 individuals and 90 413 received the usual reminder. The primary outcome was the proportion of people adequately screened and its variation by quintile of Index of Multiple Deprivation. Data were analysed by logistic regression with conservative variance estimates to take account of cluster randomisation. Results: There was a small but statistically significant (P=0.001) increase in participation with the enhanced reminder (25.8% vs 25.1%). There was significant (P=0.005) heterogeneity of the effect by socioeconomic status with an 11% increase in the odds of participation in the most deprived quintile (from 13.3 to 14.1%) and no increase in the least deprived. We estimated that implementing the enhanced reminder nationally could result in up to 80 more people with high or intermediate risk colorectal adenomas and up to 30 more cancers detected each year if it were implemented nationally. The intervention incurred a small one-off cost of £78 000 to modify the reminder letter. Conclusions: The enhanced reminder increases overall uptake and reduces the socioeconomic gradient in bowel cancer screening participation at little additional cost.