Thirty-three trials were included. Sample sizes ranged from 76 to 13,215 participants.
Faecal occult blood test: TREND results – all 10 trials described their eligibility criteria and included negative findings. All but one described their methods of recruitment; none described the activities to increase participation. Four trials reported generalisability, and four scored 19 out of 20. Positive findings (higher test completion rates with the intervention) were reported in six trials; the interventions varied widely, and five were patient directed. Negative findings were reported in two trials that had quite active comparators. One trial reported that its intervention was effective for men, but not for women.
Endoscopy: TREND results – few of the seven trials described their activities to increase adherence. Six described their methods of recruitment and eligibility criteria. Five reported on generalisability. Significant effects favouring the intervention were reported in two colonoscopy trials and two flexible sigmoidoscopy trials. One trial found significant effects on the outcome of a complete diagnostic evaluation, defined as a colonoscopy or combined flexible sigmoidoscopy plus barium enema X-ray. There were no significant differences between groups in the remaining two trials. The interventions with significant effects were all directed at patients.
More than one test: TREND results – five of the sixteen trials described their activities to increase adherence. Twelve trials described their eligibility criteria. Fourteen reported on generalisability, and methods of recruitment. Significant effects favouring the intervention were reported in nine trials; the interventions varied, and seven were patient directed. Negative findings were reported in six trials.