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).

Methods: 164 subacute LBP patients 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 €, B 5990 €) than in C (C 9510 €) (A vs. C, p=0.04 and B vs. C, n.s). 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, n.s). The perceived risk for not recovering was the strongest modifier of treatment effect. Mental & 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.