Are prognostic indicators for poor outcome different for acute and chronic low back pain consulters in primary care?

Few studies have investigated whether prognostic indicators, which contribute to the transition from acute to chronic low back pain (LBP), are also those which contribute to continuing persistence of chronic LBP. We compared the contribution of physical, psychological and social indicators to predicting disability after one year between consulters with LBP of less than 3 months duration and more than 3 months duration. Data from two large prospective cohort studies of consecutive patients consulting with LBP in general practices were merged, providing complete data for 258 cases with acute/subacute LBP and 668 cases with chronic LBP at 12 months follow-up. There were significant differences between the two LBP groups in baseline characteristics and clinical course of disability, assessed by Roland Morris Disability Questionnaire, during the year of follow-up. Adjusted associations between potential prognostic indicators and disability at 12 months were carried out in the two LBP subgroups. The final multivariable regression models showed that being non-employed, having widespread pain, a high level of Chronic Pain Grade, and catastrophising were the strongest prognostic indicators for disability at 12 months in both LBP groups. Fear of pain was significantly associated with disability in chronic LBP. Importantly, beyond baseline disability, the effect size of the other prognostic indicators for poor outcome was rather low. These findings must continue to challenge researchers to identify useful early predictors of outcome in persons with disabling back pain, as screening and targeted treatment approaches are dependent upon prognostic indicators with clinical significance.