Eligible RCT | RCT comparison | Number of participants results are based on |
---|---|---|
Meta-analysis of incentive strategies | ||
Cockayne (2005) [9] | Addition of offer of non-monetary incentive versus no offer | 1038 |
Brown (1997) [8] | Entry into a prize draw versus no entry into a prize draw | No data available |
Gates (2009) [14] | Monetary incentive versus no incentive | 2144 |
Khadajesari (2011) (a) [15] | Addition of offer of monetary incentive/ entry into prize draw/monetary donation to charity with reminder email versus no offer with reminder email | 1837 |
Khadajesari (2011) (b) [15] | Addition of offer of monetary incentive with reminder email versus no offer with reminder email | 2591 |
Bailey 1 | Addition of £20 voucher versus addition of £10 voucher | 417 |
Bailey 2 | Addition of £10 voucher plus offer of £10 voucher versus addition of £5 plus offer of £5 | 485 |
Total | 8521 | |
Meta-analysis of communication strategies | ||
Marson (2007) [12] | Enhanced letter versus standard letter | 1815 |
Nakash 2007 [11] | Additional reminder versus usual follow-up procedures | 298 |
Ashby 2011 [10] | Additional reminder versus usual follow-up procedures | 148 |
MacLennan [13] | Additional reminder versus usual follow-up procedures | 753 |
Mitchell | Pre contact and participant up-date via newsletters | No data available |
Severi (2011) (a) [16] | Text message reminder plus a fridge magnet versus standard follow-up | 1950 |
Severi (b) (2011) [16] | Reminder telephone call from principal investigator versus standard follow-up | 127 |
Total | 5091 |