Prognosis of subacute low back pain patients according to pain response.

Centralization of referred pain or failure to centralize has in earlier studies been shown to be a predictor of low back pain prognosis. Research suggests that there are differences in how males and females experience pain. The aim of this study was to evaluate the outcome after 1 year, and to evaluate the prognostic value of the pain response in a mechanical test at the first consultation at a spine clinic, and the influence of gender, in order to identify patients with especially high risk of chronicity. The patients in this study were low back pain patients, included consecutively from a spine clinic in Northern Denmark. The criteria for entering this spine clinic were neck or low back pain with radiating symptoms and a duration of 4-26 weeks, without satisfactory improvement after treatment in the primary care system. The 793 patients were categorised into four subgroups according to their pain response in a mechanical test performed at the initial examination: centralization, non-lasting centralization, peripheralization and no effect. The patients were instructed in doing specific exercises according to the test results. The four subgroups were compared after 1 year with regard to changes in back and leg pain, disability and return-to-work status. The statistical evaluation was undertaken for the study group as a whole and stratified according to gender. A significant improvement in all outcome measures was found in all the subgroups, among both men and women. There were no systematic or statistically significant differences in the prognosis between the four subgroups of patients. The proportion of Centralizers in this study was 18%. The mechanical test at baseline is important for deciding the subject-specific exercises, but when treated according to test results, the prognostic value of the test seems limited.