2. Data collection (Category A).
| Sub‐domains | Study ID | Intervention | Control |
| 1A. Questionnaire design: Questionnaire length | |||
| Dorman 1997 | New questionnaire (Shorter version) |
Standard questionnaire | |
| Edwards 2004 | New questionnaire (Shorter version) |
Standard questionnaire | |
| Subar 2001 | New questionnaire (Shorter version) |
Standard questionnaire | |
| 2A. Questionnaire design: Addition of a diary to usual follow‐up | |||
| Griffin 2019 | Diaries follow‐up | Postal questionnaires follow‐up | |
| Marques2013 | Resource use log to prospectively record their use of health services | No resource use log | |
| 3A. Questionnaire design: Question order, condition first vs generic first question | |||
| McColl 2003 | Condition‐specific measures of quality of life preceded generic instruments | Questionnaires in a reverse order | |
| 4A. Data collection frequency and timing: Timing of questionnaire delivery | |||
| Renfroe 2002 | Timing of postal questionnaire, cover letter signatory, express | Regular mail, non‐monetary incentive | |
| 5A. Data Collection Location and Method: Postal follow‐up vs clinic follow‐up | |||
| Greig 2017 | Postal follow‐up | Clinic follow‐up | |
| 6A. Data Collection Location and Method: Telephone follow‐up vs postal questionnaire | |||
| Couper 2007 | Telephone follow‐up | Postal questionnaire | |
| Marsh 1999 (Postal trial) | Postal follow‐up with an incentive | Postal follow‐up without incentive | |
| Marsh 1999 (Telephone trail) | Telephone follow‐up with an incentive | Telephone follow‐up without incentive | |
| 7A. Data Collection Location and Method: First class vs second class outward mailing | |||
| Sharp 2006 | First‐class post | Second class | |
| 8A. Data Collection Location and Method: Return postage | |||
| Sharp 2006 | Preaddressed second class stamped envelope | Business reply envelope | |
| Kenton 2007 | 'high priority' stamp to the mailing | Business format mailing | |
| Dinglas 2015 (Mail trial) | Personalised postal follow‐up | Generic postal follow‐up | |
| 9A. Data Collection Location and Method: Use of self‐sampling kits | |||
| Tranberg 2018 | Received a modified second reminder, a leaflet, and a self‐sampling kit. | received the same material as those in the directly mailed group but received no kit | |