Table 2 Effect of strategies that involved a change in mode of data collection
Study ID | Study design | Comparator | Intervention | Difference in response rate (primary end point) | Difference in response rate (secondary end point) |
|---|---|---|---|---|---|
Johnson 2015 [28] | Before and after study | Unique hyperlink to the follow-up questionnaire plus reminders sent at 2-week intervals (6 months after randomisation) | Telephone follow-up to non-resonders (4 weeks later) | Retention before telephone follow-up was 62.1% (520/837) and 82.8% (693/837) afterward: an increase of 20.7% (173/837) | No secondary end point reported |
Childs 2015 [26] | Before and after study | 3-monthly web-based surveys sent 2 years following completion of the assigned intervention | A telephone follow-up to non-responders at the end of the first year | Adding the telephone call center resulted in an 18.6% increase in follow-up rate | No secondary end point reported |
Dormandy 2008 [27] | Before and after study | Postal questionnaire completion only | A choice of telephone or postal questionnaire completion | The response rate (11 months after randomisation) from women offered postal completion was 26% compared with 67% for women offered a choice of telephone or postal completion (41% difference). Response rate for women choosing telephone completion was 98% compared with 23% for women choosing postal completion (75% difference, 95% CI diff 70 to 80) | No secondary end point reported |
Lall 2012 [29] | Prospective cohort study | Postal questionnaire completion 12 months after randomisation. | Telephone follow-up to nonrespondents (6 weeks later) | The overall response rate increased by 14% (from 71 to 85%) after telephone follow-up | No secondary end point reported |
Atherton 2010 [25] | Prospective cohort study | Postal questionnaire completion after 12 months | Online questionnaire | The response rates to the 12-month questionnaire in the online and postal groups were 51% and 29%, respectively, 4 weeks after follow-up commenced (RR 1.78 (1.47 to 2.14)) | The response rates to the 12-month questionnaire in the online and postal groups were 72% and 59%, respectively, after 3 months |
Peterson 2012 [30] | Post hoc analysis method | Routine follow-up | Home follow-up | Home follow-up (6 months after randomisation) was effective in achieving follow-up on an additional 61 participants (25%), decreasing attrition rate to only 4% | No secondary end point reported |