Table 1 Description of the baseline characteristics and outcome variables collected in the three cohorts of participants
Content validity cohort | GLA:D® Back cohort | Test–retest cohort | |
|---|---|---|---|
Baseline characteristics | |||
Age, years | ✓ | ✓ | ✓ |
Sex, male/female | ✓ | ✓ | ✓ |
Education: no qualification; public school; high school; vocational training; higher education < 3 years; higher education 3–4 years; higher education > 4 years | ✓ | ✓ | ✓ |
Back pain intensity: Numeric rating scale 0–10 (0 = no pain, 10 = worst imaginable pain) [25] | ✓ | ✓ | ✓ |
Leg pain intensity: Numeric rating scale 0–10 (0 = no pain, 10 = worst imaginable pain) [25] | ✓ | ✓ | ✓ |
Episode duration (5 -point scale): 0–2 weeks, 2–4 weeks, 4–12 weeks, 3–12 months, > 1 year | ✓ | ✓ | ✓ |
Previous back pain episodes (4-point scale): 0 episodes, 1 episode, 2–3 episodes, > 3 episodes | ✓ | ✓ | ✓ |
STarT Back Tool (SBT): Contains 9 items each with a score of 0 or 1 with a higher score indicating higher risk of poor prognosis. Risk groups are based on the total score and a sub score (Q5-9): Low risk (3 or less on the total score), medium risk (4 or more on total score and 3 or less on sub score) and high risk (4 or more on both total score and sub score) [26, 27] | ✓ | ✓ | |
Outcome measures | |||
Pain-related disability | |||
Oswestry Disability Index (ODI): Contains 10 items (pain intensity, personal care, lifting, walking, sitting, standing, sleeping, sex life, social life, traveling) each with 6 response options on a 0–5 point scale. The answers on the 10 items are converted into a single score (0–100), higher scores indicate more disability [28,29,30] | ✓ | ✓ | |
Mental health | |||
Brief Illness Perception Questionnaire (BIPQ): Contains 9 items each assessing one dimension of illness perception (consequences, timeline, personal control, treatment control, identity, illness concern, coherence, emotional representation and a causal item). Item 1–8 are scored on a 11-point scale (0–10) and converted to a sum score (range 0–80), higher scores reflects more threatening view of the back pain [31, 32] For analysis of single items (3 and 7) the response categories were reversed, and a lower score reflected a more threatening view of the back pain | ✓ | ||
Fear-Avoidance Beliefs Questionnaire (FABQ) – physical activity subscale: Contains 5 items with Likert response options scored on a 0–6 point scale (0 = Completely disagree, 6 = completely agree) of which item 2–5 are included in the score (range 0–24). Higher scores indicate higher fear avoidance beliefs [33, 34] | ✓ | ||
SF-36 subscale ‘mental health’: Contains 5 items on a 1–6 point scale (1 = All of the time, 6 = None of the time), which are converted into a single score (0–100). Higher scores indicate a more favorable mental health [35, 36] | ✓ | ||
Quality of life | |||
SF-36 subscale ‘social functioning limited by physical health’: Contains 1 item on a 1–6 point scale (1 = All of the time, 0 = None of the time). Higher scores indicate a more favorable social functioning [35, 36] | ✓ |