Characteristics of included incentive trials
| Trial | Number randomised | Disease/condition | Participant(s) | Setting | Intervention(s) | Control | Outcome retention trial | Time point used in analysis |
|---|---|---|---|---|---|---|---|---|
| Addition of monetary incentive vs none | ||||||||
| Bauer 2004 (ab) | 300 | Treatment smoking dependence | Smokers | US community | (a) $10 cheque (b) $2 cheque Arms combined | No cheque | DNA specimen kit return plus postal questionnaire response | Overall number of kits returned |
| Gates 2009 | 2144 | Treatment neck injury | Patients with whiplash injury | UK hospital trusts | £5 voucher | No voucher | Postal questionnaire response at 2 weeks | 2 week response |
| Kenyon 2005 | 722 | Treatment preterm labour | Women 7 years post-participation in ORACLE trial | UK secondary care/community | £5 voucher | No voucher | Postal questionnaire response | Overall response |
| Addition of offer of monetary incentive/prize draw vs none | ||||||||
| Khadjesari 2011 (1ac) | 1022 | Treatment alcohol dependence | Adults scoring +5 on Audit C | UK Community: web based | (a) Offer £5 voucher, (c) Offer entry £250 prize draw Arms combined | No offer | Web-based questionnaire response | Response within 40 days of first reminder |
| Khadjesari 2011 (2) | 2591 | Treatment alcohol dependence | Adults scoring +5 on Audit C | Community: web based | Offer £10 Amazon voucher | No offer | Web-based questionnaire response | Response within 40 days of first reminder |
| Addition of non-monetary incentive vs none | ||||||||
| Bowen 2000 (abc) | 4728 | Prevention lung cancer | Adults exposed to smoking and asbestos | US sites | (a) Certificate, (b) pin, (c) pin and certificate Arms combined | No certificate/pin | Trial retention | Time from randomisation to first inactivation (stop taking vitamins or placebo) during PRIDE 2 year follow-up |
| Renfroe 2002 (a) | 664 | Treatment ventricular fibrillation ventricular tachycardia | Adults cardioverted from VT or resuscitated from VF | US hospital | Certificate of appreciation | No certificate | Postal questionnaire response | Overall response |
| Sharp 2006 (a) | 231 | Screening cervical cancer | Women with low-grade abnormal cervical smear | UK primary care | Pen | No pen | Postal questionnaire response | Overall response |
| Sharp 2006 (b) | 232 | Screening cervical cancer | Women with low-grade abnormal cervical smear | UK primary care | Pen | No pen | Postal questionnaire response | Overall response |
| Sharp 2006 (c) | 233 | Screening cervical cancer | Women with low-grade abnormal cervical smear | UK primary care | Pen | No pen | Postal questionnaire response | Overall response |
| Sharp 2006 (d) | 234 | Screening cervical cancer | Women with low-grade abnormal cervical smear | UK primary care | Pen | No pen | Postal questionnaire response | Overall response |
| Addition of offer of non-monetary incentive vs no offer | ||||||||
| Cockayne 2005 | 1038 | Prevention fracture | Women with hip fracture risk factors | UK primary care | Offer of study results | No offer | Postal questionnaire response | Overall response |
| Hughes 1989 | 100 | Treatment smoking dependence | Adult smokers | US community | Offer results reprint | No offer | Postal questionnaire response | Overall response |
| Addition of offer of monetary donation to charity vs no offer | ||||||||
| Khadjesari 2011 (1b) | 815 | Treatment alcohol dependence | Adults scoring +5 on Audit C | Community: on line | Offer £5 charity donation | No offer | Web-based questionnaire response | Response within 40 days of first reminder |
| Addition of £10 plus offer of £10 vs addition of £5 plus offer of £5 | ||||||||
| Bailey (2) (unpublished) | 417 | Promotion sexual health | Young people | Community UK on line | Offer of £20 shopping voucher | Offer of £10 shopping voucher | Postal questionnaire response | Response at 3-month follow-up |
| Addition of £20 voucher offer vs addition of £10 voucher offer | ||||||||
| Bailey (1) (unpublished) | 485 | Promotion of sexual health | Young people | Community UK on line | £10 shopping voucher + offer of £10 shopping voucher | £5 shopping voucher + offer of £5 shopping voucher | Postal questionnaire response and chlamydia kit return | Response at 3-month follow-up |
| Addition of monetary incentive vs offer of entry into prize draw | ||||||||
| Kenton 2007 (a) | 147 | Prevention of postnatal depression | Women postpartum at high risk of postnatal depression | Canada community | $2 coin | Draw for $50 gift voucher | Postal questionnaire response | Overall response |
| Kenton 2007 (b) | 150 | Prevention of postnatal depression | Women postpartum at high risk of postnatal depression | Canada community | $2 coin | Draw for $50 gift voucher | Postal questionnaire response | Overall response |
| Offer of prize draw entry vs no offer | ||||||||
| Leigh Brown 1997 | 1307 | Clinical management of orthopaedic conditions | Adults non-surgical musculoskeletal conditions | UK hospital out patients department | Aware offer of monthly prize draw of £25 gift voucher | No offer | Postal questionnaire response after 1st and 2nd reminder | No data available |