Behavioural interventions to increase uptake of FIT colorectal screening in Scotland (TEMPO): a nationwide, eight-arm, factorial, randomised controlled trial

Background Uptake of colorectal cancer screening is suboptimal. The TEMPO trial evaluated the impact of two evidence-based, theory-informed, and co-designed behavioural interventions on uptake of faecal immunochemical test (FIT) colorectal screening. Methods TEMPO was a 2 x 4 factorial, eight-arm, randomised controlled trial embedded in the nationwide Scottish Bowel Screening Programme. All 40 000 consecutive adults (aged 50-74 years) eligible for colorectal screening were allocated to one of eight groups using block randomisation: (1) standard invitation; (2) 1-week suggested FIT return deadline; (3) 2-week deadline; (4) 4-week deadline; (5) problem-solving planning tool (no deadline); (6) planning tool plus 1-week deadline; (7) planning tool plus 2-week deadline; (8) planning tool plus 4-week deadline. The primary outcome was the proportion of FITs returned correctly completed to be tested by the colorectal screening laboratory providing a positive or negative result, within 3 months of the FIT being mailed to a person. The trial is registered with clinicaltrials.gov, NCT05408169. Findings From June 19 to July 3, 2022, 5000 participants were randomly assigned per group, with no loss to follow-up. 266 participants met the exclusion criteria; 39 734 (19 909 [50<middle dot>1%] female and 19 825 [49<middle dot>9%] male; mean age 61<middle dot>2 [SD 7<middle dot>3] years) were included in the analysis. The control group (no deadline, and no planning tool) had a 3-month FIT return rate of 66<middle dot>0% (3275 of 4965). The highest return rate was seen with a 2-week deadline without the planning tool (3376 [68<middle dot>0%] of 4964; difference vs control of 2<middle dot>0% [95% CI 0<middle dot>2 to 3<middle dot>9]). The lowest return rate was seen when the planning tool was given without a deadline (3134 [63<middle dot>2%] of 4958; difference vs control of -2<middle dot>8% [-4<middle dot>7 to -0<middle dot>8]). The primary analysis, assuming independent effects of the two interventions, suggested a clear positive effect of giving a deadline (adjusted odds ratio [aOR] 1<middle dot>13 [1<middle dot>08 to 1<middle dot>19]; p<0<middle dot>0001), and no effect for use of a planning tool (aOR 0<middle dot>98 [0<middle dot>94 to 1<middle dot>02]; p=0<middle dot>34), though this was complicated by an interaction between the two interventions (p(interaction)=0<middle dot>0041); among those who were given a deadline, there was no evidence that receiving a planning tool had any effect (aOR 1<middle dot>02 [0<middle dot>97 to 1<middle dot>07]; p=0<middle dot>53), but in the absence of a deadline, giving the planning tool appeared detrimental (aOR 0<middle dot>88 [0<middle dot>81 to 0<middle dot>96]; p=0<middle dot>0030). In the absence of the planning tool, there was little evidence that the use of a deadline had any effect on return rates at 3 months. However, secondary analyses indicated that the use of deadlines boosted earlier return rates (within 1, 2, and 4 weeks, particularly around the time of the deadline), and reduced the need to issue a reminder letter after 6 weeks, with no evidence that the planning tool had any positive impact, and without evidence of interactions between interventions. Interpretation Adding a single sentence suggesting a deadline for FIT return in the invitation letter to FIT colorectal screening resulted in more timely FIT return and reduced the need to issue reminder letters. This is a highly cost-effective intervention that could be easily implemented in routine practice. A planning tool had no positive effect on FIT return. Funding Scottish Government and Cancer Research UK. Copyright (c) 2025 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.