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Table 4 Delphi survey research priorities for assessing the effectiveness of missing data interventions

From: Identifying research priorities for effective retention strategies in clinical trials

Scores Round 1 Round 2 Ranking
Missing data intervention %1–3 %4–6 %7–9 %1–3 %4–6 %7–9
Site initiation training on missing dataa 6% 19% 75% 6% 11% 83% 1
Frequency of patient contact during the triala 3% 31% 66% 0% 21% 79% 2
Use of routinely collected dataa 6% 22% 72% 6% 17% 77% 3
Frequency and timing of remindersa 0% 34% 66% 0% 24% 76% 4
Triggered site training on missing dataa 6% 31% 64% 3% 23% 74% 5
Length/time needed to complete the questionnairea 11% 28% 61% 9% 17% 74% 6
Frequency of contact between central trial staff and investigators 11% 31% 58% 6% 26% 69% 7
Impact of site recruitment rates on data collection 9% 31% 60% 9% 23% 69% 8
Postal or online questionnaires 3% 39% 58% 3% 31% 66% 9
Frequency of questionnaires 6% 36% 58% 6% 29% 66% 10
Data collection scheduled with routine care 8% 31% 61% 9% 26% 66% 11
ONS flagging of patients 15% 27% 58% 16% 19% 66% 12
Impact of local site researcher/clinical staff continuity 6% 34% 60% 3% 32% 65% 13
Telephone reminders 9% 34% 57% 9% 26% 65% 14
Contacting GPs for missing data or to trace patients 17% 31% 51% 9% 26% 65% 14
Only collecting the primary outcome for patients with missing primary and secondary data 6% 32% 62% 6% 30% 64% 16
Email reminders 0% 45% 55% 3% 34% 63% 17
Patient data entry, e.g. use of mobile phone applications (apps), online data or other systems 9% 34% 57% 6% 32% 62% 18
Staggered per patient payments based on patient progress and data collection 9% 29% 63% 9% 29% 62% 19
A timeline reminder of participant visits for sites 11% 37% 51% 9% 32% 59% 20
Flexibility in appointment times, e.g. data collection window 6% 42% 53% 6% 37% 57% 21
Site selection strategies 11% 37% 51% 11% 31% 57% 22
Questionnaires completed in the presence of researchers/clinical staff 11% 39% 50% 11% 31% 57% 22
Case management, e.g. arranging appointments and helping patients access health care 19% 35% 45% 20% 23% 57% 24
Re-imbursement of participant expenses 11% 37% 51% 6% 38% 56% 25
Postal reminders 11% 40% 49% 9% 35% 56% 26
Questionnaires returned to local sites vs central office, e.g. is monitoring of response rates and follow-up of missing questionnaires best performed by local sites or central trial offices 9% 37% 54% 9% 35% 56% 26
Data collected by phoning the patient 11% 37% 51% 9% 37% 54% 28
Inclusion of prepaid envelope 22% 36% 42% 23% 26% 51% 29
SMS text reminders 12% 45% 42% 13% 38% 50% 30
Teleconference meetings with investigators 11% 42% 47% 9% 43% 49% 31
Clinician/researcher-collected outcomes versus PROMS (patient-reported outcome measures) NA NA NA 13% 41% 47% 32
Location where questionnaires are completed, e.g. home or clinic 8% 42% 50% 9% 46% 46% 33
Retention and withdrawal information within the Patient Information Sheets 14% 42% 44% 14% 40% 46% 34
Follow-up through patient notes only 14% 43% 43% 9% 47% 44% 35
Research nurse teleconferences or face-to-face meetings NA NA NA 3% 54% 43% 36
Use of social media to contact participants 13% 47% 41% 10% 48% 42% 37
Flexibility in appointment locations, e.g. home or clinic 14% 39% 47% 14% 46% 40% 38
Site newsletters 11% 44% 44% 14% 49% 37% 39
Availability of blinded outcome assessors to ensure data availability and quality NA NA NA 29% 35% 35% 40
Routine site visits by CTU staff 8% 53% 39% 3% 63% 34% 41
Timing of sending questionnaires, e.g. before or shortly after a visit 11% 51% 37% 9% 57% 34% 42
Collecting multiple contact details for participants 24% 38% 38% 24% 42% 33% 43
Face-to-face meetings with investigators 6% 58% 36% 6% 63% 31% 44
Patient diaries to collect data 11% 50% 39% 14% 54% 31% 45
Total Design Method (Dillman [31]), a specific approach to maximise questionnaire response rates that utilises cover letters, reminders and resending questionnaires 16% 44% 41% 16% 53% 31% 46
Behavioural motivation strategies, e.g. workshop for patients to help facilitate completion of intervention and follow-up 24% 45% 30% 30% 42% 27% 47
Format of newsletters and mode of delivery NA NA NA 12% 62% 26% 48
Offer of trial results for participants 11% 58% 31% 11% 63% 26% 49
Frequency of newsletters 8% 64% 28% 6% 74% 20% 50
Question order, e.g. health-related, generic or medical questions first 11% 61% 28% 6% 74% 20% 50
Patient newsletters 16% 59% 25% 13% 68% 19% 52
Open trial design 41% 44% 15% 42% 45% 13% 53
Timing of monetary/gift voucher for participants, e.g. given conditionally on completion of assessment or unconditionally at the beginning or end of trial 29% 47% 24% 27% 61% 12% 54
Monetary incentives or gift voucher incentives for participants 29% 44% 26% 30% 58% 12% 55
Transport to and from appointments 14% 63% 23% 15% 76% 9% 56
Taking contact details for friends/family of participants 31% 50% 19% 32% 61% 6% 57
Gift for participant 42% 45% 13% 42% 52% 6% 58
Prize draw limited to trial participants 41% 44% 16% 34% 59% 6% 59
Enhanced cover letter 24% 55% 21% 21% 73% 6% 60
Trial certificate 44% 50% 6% 50% 44% 6% 61
Trial website 31% 53% 17% 26% 69% 6% 62
The use of a Freephone number for updating participant’s contact details 35% 58% 6% 40% 57% 3% 63
Trial identity cards 39% 52% 10% 42% 55% 3% 64
Use of social media to contact site staff 33% 55% 12% 38% 59% 3% 65
Gift for site staff 45% 52% 3% 36% 61% 3% 66
Christmas and/or birthday cards for participants 48% 45% 6% 64% 33% 3% 67
Type of post used, e.g. priority, standard or recorded post 34% 54% 11% 29% 68% 3% 68
Personal touch, e.g. handwritten letter or addition of post it notes 26% 71% 3% 27% 73% 0% 69
Offer of a crèche service 50% 46% 4% 57% 43% 0% 70
Christmas cards for site staffb 67% 33% 0% 82% 18% 0% 71
  1. aConsensus was achieved that the future research was of critical importance. bConsensus was achieved that future research was not important
  2. CTU Clinical Trial Unit, GP general practitioner, NA not applicable, ONS Office for National Statistics, SMS short message service