Table 1

Initial measurement of predictor variables

 Predictor How will be measured How will be coded Duration of current episode (days) How many days ago did your back pain start?* 7–10; 11–14; 15–23; 24–49 Number of previous episodes How many previous episodes of low back pain have you had?27 0; 1–2; 3–8s; >9 Depression How much have you been bothered by feeling depressed in the past week? Measured on a 0–10 scale where 0=not at all and 10=extremely28 0 depression score; 1–3 depression score; 4–6 depression score; 7–10 depression score Pain intensity Using Numeric Pain RatingScale (NPRS)29: I would like you to rate your pain on a scale from 0 to 10 where 0 is no pain and 10 is the worst possible pain. Please give a number to describe your average pain over the last24 hours.30 Mild: 2–4; moderate: 5–7; severe: 8–10 Pain intensity change from first visit to 1-week review as an absolute value Calculated by subtracting theNPRS at day 1 from NPRS at ‘1-week review’ Worse: ≤−2; not much change: −1,0, 1; small change: 2, 3; moderate and large change: ≥4
• All predictor variables will be measured at initial presentation for care except for the pain intensity (collected at the first weekly follow-up) and pain intensity change variables.

• *Seven days will be added to duration of current episode collected at initial presentation to reflect the duration of episode at 1-week review.