Table 3.
Variables, measures and their characteristics
| Variable | Measure | Items | Details | Reliability where available | Administration point, trial arms |
|---|---|---|---|---|---|
| Pain duration | Pain duration38 | 1 | This single item asks ‘how long it was since you had a whole month without pain’. Response options range from ‘less than 3 months’ to ‘over 10 years’38 | Baseline All arms |
|
| Back-specific physical disability | RMDQ31 | 24 | Patients select from a list of items that may describe their experience on the day of scale completion (eg, ‘I sleep less well on my back’). The scale is dichotomous, patients select whether the symptom is present or not | Internal consistency: 0.77–0.9339 | Baseline, follow-up All arms |
| Pain intensity | Pain index created by three numerical rating scales40 | 3 | Patients rate their current pain, average and least pain over the past 2 weeks on three 11-point rating scales | Test-retest reliability: 0.67–0.9641 | Baseline, follow-up All arms |
| Days in pain | Number of troublesome days in pain over the last month | 1 | Based on a measure used by Little et al,42 this single item asks patients to record the number of troublesome days they have spent in pain over the last month | Baseline, follow-up All arms |
|
| Risk of persistent disability | SBST40 | 9 | Patents indicate whether they disagree or agree with items covering modifiable prognostic indicators including bothersomeness, disability and mood. Patients are asked to respond thinking about their past 2 weeks | Internal consistency: 0.7940 |
Baseline, follow-up All arms |
| Fear of movement | TSK43 | 17 | Patients rate agreement with items including ‘I'm afraid I will injure myself if I exercise’. Items are scored from 1 to 4, ranging from strongly disagree to strongly agree | Internal consistency range: 0.70–0.7944 | Baseline, follow-up All arms |
| Negative orientation toward pain | PCS45 | 13 | Patients indicate their agreement with items following the stem ‘When I'm in pain…’ Items include ‘I feel like I can't go on’ and are scored on a scale of five-point scale ranging from ‘not at all’ to ‘all of the time’ | Internal consistency: 0.8146 | Baseline, follow-up All arms |
| Physical activity | Short form IPAQ47 | 7 | Patients provide time spent walking, undertaking vigorous and moderate activity, as well as time spent sedentary over the past 7 days | Test-retest reliability range: 0.65–0.8847 | Baseline, follow-up All arms |
| Enablement coping/satisfaction | Modified PEI48 | 6 | Patients are asked to consider the healthcare they have received in the past 3 months and rate items including ‘I am able to cope better with my back problem’ and ‘I am able to understand my back problem better’. Items are scored on a seven-point scale from strongly agree to strongly disagree | Internal consistency: 0.9248 | Baseline, follow-up All arms |
| Quality of life | EuroQol EQ-5D49 | 6 | The EQ-5D consists of two parts. Part 1 consists items on five domains, for example, mobility, self-care. Part 2 features a VAS that records patient's ratings of overall health | Baseline, follow-up All arms |
|
| LBP-related health care resource use | Measured with a brief questionnaire developed for this trial | 10 | LBP resource use measured will include medication use, number of GP visits, other NHS care and private LBP related-therapy costs | Follow-up All arms |
|
| Time off work | Measured with a single item developed for this trial | 1 | Patients are asked how much time they have had off work in the past 3 months | Follow-up All arms |
|
| Beliefs about effectiveness and credibility of the interventions | Modified CEQ50 51 | 6 2 |
Patients rate the extent they think/ feel the intervention is likely to improve their back pain-related functioning, and credibility. Items range from 1 not at all to 9 very much. Two items measuring how patients think and feel about likely improvement are measured as a percentage. Two items drawn from the expectancy section of the questionnaire will be asked to all patients |
Internal consistency range: 0.82–0.8450 | Following session 1 Internet intervention arms only Baseline All arms |
| Exercise self-efficacy | Modified Self-Efficacy for Exercise scale52 53 | 8 | Patients rate how confident they are on a scale between 0 and 10 that they could complete activities suggested by the internet intervention in the face of obstacles such as ‘if they felt pain’, ‘if they were bored’ and ‘if they were depressed’ | Internal consistency: 0.9253 | Following session 1 Internet intervention arms only |
| Reasons for non-adherence | PETS54 | 18 | The scale is designed specifically to measure reasons for patient non-adherence to home-based rehabilitation. Patents rate their agreement with items on a five-point scale across domains including problems with symptoms, uncertainty, doubts, practicalities and lack of support | Internal consistency for the PETS subscales range: 0.84–0.9654 | Follow-up All arms |
| Adherence to specific activities for LBP | Items developed specifically for this study | 4 | Patients are asked about the number of weeks if any they may have walked and/or engaged gentle back exercises. They are also asked estimate of how many days a week they went for walks and/or did gentle back exercises. Patients are also asked if they stopped activities because they no longer are experiencing pain | Follow-up All arms |
CEQ, Credibility and Expectancy Questionnaire; GP, general practitioner; IPAQ, International Physical Activity Questionnaire; LBP, low back pain; NHS, National Health Service; PCS, Pain Catastrophising Scale; PEI, Patient Enablement Instrument; PETS, Problematic Experiences of Therapy Scale; RMDQ; Roland-Morris Disability Questionnaire; SBST, STarT Back Screening Tool; TSK, The Tampa Scale for Kinesiophobia; VAS, Visual Analogue Scale.