Summary of intervention typology and quality appraisal
| Intervention category | Intervention type | Positive effect (high bias) | No effect (high bias) | Strength of evidence |
|---|---|---|---|---|
| GP education | Peer review and training/feedback | 4 (1) | 0 | i |
| GP training: professional development | 10 (1) | 7 (2) | iii | |
| Guidelines (no training/feedback) | 7 (2) | 5 | iii | |
| Guidelines with training/feedback/specialist support | 11 | 6 | iii | |
| Process change | Designated appointment slots/fast-track clinic | 4 (1) | 2 | iii |
| Direct access to screening/diagnostic testing | 6 | 3 | iii | |
| Specialist consultation before referral | 11 (3) | 0 | i | |
| Electronic referral | 9 (1) | 1 | i | |
| Decision support tool | 6 | 4 | iii | |
| Waiting list review | 1 | 2 | iii | |
| System change | Additional primary care staff | 0 | 3 (1) | i (−ve) |
| Community provision of ‘specialist’ services by GPs | 7 | 2 (1) | i | |
| Outreach: community provision by specialists | 8 | 2 (1) | i | |
| Return of inappropriate referrals | 2 (1) | 0 | ii | |
| Gatekeeping | 0 | 4 (1) | iii | |
| Payment system | 1 | 3 (1) | iii | |
| Referral management centre | 3 (2) | 3 | iii | |
| Patient inventions | Patient education | 1 | 1 | iii |
| Patient concerns and satisfaction | 1 | 0 | iii | |
i = stronger evidence. ii = weaker evidence. iii = conflicting or no evidence (evidence from one study). [–ve] = negative affect on referral outcomes. Adapted from the method of Hoogendoorn et al 1999.