Mini-intervention for subacute low back pain: two-year follow-up and modifiers of effectiveness.

STUDY DESIGN: Randomized controlled trial.

OBJECTIVES: To Investigate the long-term effectiveness, costs, and effect modifiers of a mini-intervention, provided in addition to the usual care, and the incremental effect of a worksite visit for patients with subacute disabling low back pain (LBP).

SUMMARY OF BACKGROUND DATA: A mini-intervention was earlier proved to be an effective treatment for subacute LBP. Whether the beneficial effect is sustained is not known. Furthermore, modifiers of a treatment effect are largely unknown.

METHODS: A total of 164 patients with subacute LBP randomized into a mini-intervention (A, n = 56), a mini-intervention plus a worksite visit (B, n = 51), or the usual care (C, n = 57). Mini-intervention consisted of a detailed assessment of the patients' history, beliefs, and physical findings by a physician and a physiotherapist, followed by recommendations and advice. The usual care patients received the conventional care. Pain, disability, health-related quality of life, satisfaction with care, days on sick leave, and health care consumption and costs were measured during a 24-month follow-up. Thirteen candidate modifiers were tested for each outcome.

RESULTS: There were no differences between the three treatment arms regarding the intensity of pain, the perceived disability, or the health-related quality of life. However, mini-intervention decreased occurrence of daily (A vs., C, P = 0.01) and bothersome (A vs. C, P < 0.05) pain and increased treatment satisfaction. Costs resulting from LBP were lower in the intervention groups (A 4670 Euros, B 5990 Euros) than in C (C 9510 Euros) (A vs. C, P = 0.04; and B vs. C, not significant). The average number of days on sick leave was 30 in A, 45 in B, and 62 in C (A vs. C, P = 0.03; B vs. C, not significant). The perceived risk for not recovering was the strongest modifier of treatment effect. Mental and mental-physical workers in A and B were less often on sick leave than those in C.

CONCLUSIONS: Mini-intervention is an effective treatment for subacute LBP. Despite lack of a significant effect on intensity of low back pain and perceived disability, mini-intervention, including proper recommendations and advice, according to the "active approach," is able to reduce LBP-related costs. The perceived risk of not recovering was the strongest modifier of treatment effect. In alleviating pain, the intervention was most effective among the patients with a high perceived risk of not recovering.