Background
Screening with the guaiac faecal occult blood test (gFOBt) is associated with improved colorectal cancer (CRC) survival, and is offered biennially to men and women aged 60–74 years in England’s national Bowel Cancer Screening Programme (BCSP). Uptake of the gFOBt is low, with only 54 % of the eligible population completing the test. Text-message reminders could improve uptake of gFOBt.

Methods/design
This paper describes the protocol for a randomised controlled trial, which will examine the effectiveness of a text-message reminder to promote uptake of gFOBt screening in the BCSP. Individual mobile telephone data from 180 general practices in London with existing mobile-health services will be linked to the national BCSP information system via a secure on-line network. All screening-eligible adults registered with a participating practice will be randomised, to receive either usual care (N = 1600) or usual care plus a text-message reminder to self-complete and return their kit eight weeks after their initial invitation (N = 1600). The primary outcome will be the proportion of individuals who return an adequately completed gFOBt kit within 18 weeks of the initial invitation. Differences in uptake between groups will be evaluated using a logistic regression analysis, adjusting for individual-level and area-level socio-demographic variables.

Discussion
This will be the first large-scale randomised trial of a text-message reminder in a national screening programme for CRC. If effective, this study provides a cost-effective means to promote uptake of CRC screening in an organised programme.

Trial registration
Current Controlled Trials ISRCTN70904476 (18/09/2015).