Theoretically-informed vs standard cover letter to improve participant response to mailed questionnaire: results of an embedded randomised retention trial

Theoretically-informed vs standard cover letter to improve participant response to mailed questionnaire: results of an embedded randomised retention trial | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Theoretically-informed vs standard cover letter to improve participant response to mailed questionnaire: results of an embedded randomised retention trial Colin Charles Everett, Sarah T Brown, Joanna L Dennett, Howard Collier, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4109848/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 Nov, 2024 Read the published version in Trials → Version 1 posted 5 You are reading this latest preprint version Abstract Background Participant non-response is a source of bias in all research, especially in randomised controlled trials. Participants followed-up remotely can have high non-response rates. Four trials have been conducted of a cover letter with content informed by behaviour-change theory to overcome hypothesised barriers to responding to a mailed questionnaire. Pooled results to date have suggested further research to be worthwhile. We conducted an embedded randomised study within a trial of such cover letters in the hope that we would improve response rates to our postal quality of life questionnaires. Methods 148 participants in the CODIFI2 diabetic foot ulcer sampling trial were randomised 1:1 to receive one of two different cover letters at follow-up visits: either a standard cover letter accompanying their postal follow-up questionnaires, or to an “enhanced” (theory-informed) cover letter. Questionnaires were mailed at 39, 52 and (for some participants) 104 weeks post randomisation. Outcome measures were response to mailing at each timepoint. Analysis was restricted to those for whom a questionnaire and letter was issued. Owing to limited recruitment, a reduced analysis plan, comprising solely observed response rates and 95% confidence intervals for difference in response rates was followed. Post hoc, we added our week 52 results to an already-published meta-analysis. Results 67/74 enhanced cover letter group (Enhanced) and 67/74 standard cover letter group (Standard) participants who had not already died or withdrawn were sent their first mailing at 39 weeks. The 39-week response rates were, 70.1% (47/67) and 58.2% (39/67) for Enhanced and Standard participants, respectively. At week 52 the response rates were 70.3% (45/64) and 55.6% (35/63) for Enhanced and Standard participants, respectively. At week 104, the response rates were 72.7% (24/33) and 57.6% (19/33) for the Enhanced and Standard participants, respectively. Adding our week 52 results to a published meta-analysis increased the pooled estimate of differences in response rates to 0.04 (-0.01 to 0.09) favouring enhanced letters. Conclusion While this embedded randomised trial observed greater response rates at all times among those randomised to the enhanced letter, the reduced trial sample size meant that these results are imprecise. Trial registration: ISRCTN74929588, registered 5th March 2019. SWAT Study within a Trial Retention Methods embedded randomised controlled trial Surveys and questionnaires behavioural change theory Diabetic Foot Follow- up Studies Quality of Life Outcome Assessment Health Care Full Text Supplementary Files CONSORTChecklist.pdf SupplementaryAppendix1Eligibility.pdf SupplementaryAppendix2CoverLetterBundle.pdf SupplementaryAppendix3Additionalbaselinechars.pdf Cite Share Download PDF Status: Published Journal Publication published 14 Nov, 2024 Read the published version in Trials → Version 1 posted Editorial decision: Minor revision 17 Jul, 2024 Reviewers agreed at journal 08 Jun, 2024 Reviewers invited by journal 02 Jun, 2024 Editor assigned by journal 17 Apr, 2024 First submitted to journal 18 Mar, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4109848","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":309692687,"identity":"20861b6e-b673-415f-a018-d6b16445c9f6","order_by":0,"name":"Colin Charles 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within a Trial, Retention Methods, embedded randomised controlled trial, Surveys and questionnaires, behavioural change theory, Diabetic Foot, Follow- up Studies, Quality of Life, Outcome Assessment, Health Care","lastPublishedDoi":"10.21203/rs.3.rs-4109848/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4109848/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBackground Participant non-response is a source of bias in all research, especially in randomised controlled trials. Participants followed-up remotely can have high non-response rates. Four trials have been conducted of a cover letter with content informed by behaviour-change theory to overcome hypothesised barriers to responding to a mailed questionnaire. Pooled results to date have suggested further research to be worthwhile. We conducted an embedded randomised study within a trial of such cover letters in the hope that we would improve response rates to our postal quality of life questionnaires.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMethods 148 participants in the CODIFI2 diabetic foot ulcer sampling trial were randomised 1:1 to receive one of two different cover letters at follow-up visits: either a standard cover letter accompanying their postal follow-up questionnaires, or to an “enhanced” (theory-informed) cover letter. Questionnaires were mailed at 39, 52 and (for some participants) 104 weeks post randomisation. Outcome measures were response to mailing at each timepoint. Analysis was restricted to those for whom a questionnaire and letter was issued. Owing to limited recruitment, a reduced analysis plan, comprising solely observed response rates and 95% confidence intervals for difference in response rates was followed. Post hoc, we added our week 52 results to an already-published meta-analysis.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eResults 67/74 enhanced cover letter group (Enhanced) and 67/74 standard cover letter group (Standard) participants who had not already died or withdrawn were sent their first mailing at 39 weeks. The 39-week response rates were, 70.1% (47/67) and 58.2% (39/67) for Enhanced and Standard participants, respectively. At week 52 the response rates were 70.3% (45/64) and 55.6% (35/63) for Enhanced and Standard participants, respectively. At week 104, the response rates were 72.7% (24/33) and 57.6% (19/33) for the Enhanced and Standard participants, respectively. Adding our week 52 results to a published meta-analysis increased the pooled estimate of differences in response rates to 0.04 (-0.01 to 0.09) favouring enhanced letters.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eConclusion While this embedded randomised trial observed greater response rates at all times among those randomised to the enhanced letter, the reduced trial sample size meant that these results are imprecise.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTrial registration: ISRCTN74929588, registered 5th March 2019.\u003c/p\u003e","manuscriptTitle":"Theoretically-informed vs standard cover letter to improve participant response to mailed questionnaire: results of an embedded randomised retention trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-17 18:54:13","doi":"10.21203/rs.3.rs-4109848/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Minor revision","date":"2024-07-18T03:43:58+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-06-08T09:17:17+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-02T22:04:53+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-17T09:31:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"Trials","date":"2024-03-18T08:54:47+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"trials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"trls","sideBox":"Learn more about [Trials](http://trialsjournal.biomedcentral.com/)","snPcode":"13063","submissionUrl":"https://www.editorialmanager.com/trls","title":"Trials","twitterHandle":"MedicalEvidence","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"01eb10da-5610-4513-ae28-e6424afe7023","owner":[],"postedDate":"June 17th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-11-18T19:28:55+00:00","versionOfRecord":{"articleIdentity":"rs-4109848","link":"https://doi.org/10.1186/s13063-024-08565-0","journal":{"identity":"trials","isVorOnly":false,"title":"Trials"},"publishedOn":"2024-11-14 15:58:16","publishedOnDateReadable":"November 14th, 2024"},"versionCreatedAt":"2024-06-17 18:54:13","video":"","vorDoi":"10.1186/s13063-024-08565-0","vorDoiUrl":"https://doi.org/10.1186/s13063-024-08565-0","workflowStages":[]},"version":"v1","identity":"rs-4109848","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4109848","identity":"rs-4109848","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}