From: Trial Forge Guidance 2: how to decide if a further Study Within A Trial (SWAT) is needed
Total number of participants | Intervention (n recruited/N invited) | Control (n recruited/N invited) | Baseline (control) recruitment rate | Effect estimate (95% CI) | |
---|---|---|---|---|---|
Bauer, 2004 [27] (Sending $10 or $2 with invitations to return DNA sample (in mouthwash). Comparator was no money. People responding were a subgroup of a smoking cessation trial population). | 300 | 77/200 | 34/100 | 34% | 5% (−7% to 16%) |
Kenyon, 2005 [28] (Sending £5 voucher with invitations to return trial follow-up questionnaire. Comparator was no money. People responding were taking part in a trial to improve neonatal outcomes). | 722 | 156/369 | 108/353 | 31% | 12% (5%–19%) |
Gates, 2009 [29] (Sending £5 voucher with invitations to return trial follow-up questionnaire. Comparator was no money. People responding were taking part in a trial to improve neck injury outcomes). | 2144 | 560/1070 | 493/1074 | 46% | 6% (2%–11%) |
Cumulative results (Bauer + Kenyon + Gates) | 3166 | 793/1639 | 635/1527 | 37% (mean) | 8% (4%–11%) |