Objectives: To investigate the influence of general practitioner (GP) endorsement on participation in screening for colorectal cancer based on a faecal occult blood test (FOBT).
Setting: South Australian residents (n=2400), in 1999, aged >50 years.
Methods: Random selection of three groups (GP1, GP2, GP3) from two general practices and of one group (ER) from the federal electoral roll; n=600 per group. Without previous communication or publicity, subjects were posted an offer of screening by immunochemical FOBT. The GP1 and ER groups were invited without indication that their GP was involved; GP2 received an invitation indicating support from the practice; and GP3 received an invitation on practice letterhead and signed by a practice partner. A reminder was posted at 6 weeks. Participation was defined as return of correctly completed FOBT sample cards within 12 weeks.
Results: Participation rates were: GP1 192/600 (32.0%), GP2 228/600 (38.0%), and GP3 244/600 (40.7%); chi(2)=10.2, p=0.006. Both GP2 and GP3 differed significantly from GP1 (odds ratio (OR) 0.77, 95% confidence interval (95% CI) 0.60 to 0.98 and relative risk (RR)=0.69, 95% CI 0.54 to 0.87 respectively). ER (193/600 (32.2%)) and GP1 were not significantly different. Age but not sex was significantly associated with participation. Overall test positivity rate was 4.6%; five malignancies were found in the 918 who performed FOBT.
Conclusions: Association of a GP of recent contact with a screening offer in the form of a personalised letter of invitation achieves better participation than does the same letter from a centralised screening unit that does not mention the GP. Thus, GP enhanced participation is achievable without their actual involvement. Additional strategies are needed to further improve participation.