Predicting the transition from acute to persistent low back pain in primary care

Abstract

Low back pain (LBP) is by far the most prevalent and costly musculoskeletal problem in our society today. Most people experience an episode of LBP at least once in their lifetime. Some of them go on to develop persistent LBP. The aim of this thesis is to identify predictors for persistent LBP in patients suffering from acute LBP.

In a systematic review screening instruments were identified showing for psychological and occupational factors the highest reliability regarding the prognosis of patients with LBP. Following the recommendations of the Multinational Musculoskeletal Inception Cohort Study (MMICS) Statement, a study protocol was developed to detect patient characteristics which increase the risk of chronicity, and to reveal the best time point for identifying patients at risk of developing persistent LBP. Acute LBP patients were recruited from general practitioner clinics in New Zealand, and assessed by postal survey at baseline and at three, six, twelve-week and six-month follow-up. Primary outcome was functional limitation measured by the Oswestry Disability Index (ODI); key secondary endpoints were pain on the Visual Analogue Scale (VAS), and general health measured by the acute Short Form 12 (SF-12).

A feasibility study was conducted of patients who had attended a health practitioner for either their first episode of acute LBP, or recurrent LBP with at least thirty LBP-free days between two episodes. The index ‘depression and maladaptive cognitions’ was found to be a significant baseline-predictor for persistent LBP up to six months.

In the main study time-related LBP characteristics correlated with prognostic factors for acute/ subacute LBP. Further findings demonstrated that patients with current LBP waiting longer till seeking care had a more disadvantageous profile of psychological and occupational risk factors, and lower resource levels. A final four-predictor model for persistent LBP, defined by functional limitation at six months included ‘resigned attitude towards the job’ and ‘social support at work’ as the strongest prognostic factors; a final two-predictor model for persistent LBP defined by pain at six months revealed ‘social support at work’ as the strongest prognostic factor. The best time points to predict the development of persistent LBP at six months were the six and twelve-week follow-up. When considering resources for preventing persistent LBP, at twelve weeks ‘social support’ was confirmed as a strong occupational protective factor – similar to findings at six months. The presence of ‘depression’ had a negative influence on the course of recovery in patients presenting with acute/ subacute LBP. ‘Depression’ together with ‘job control’ and ‘functional limitation’ were also baseline-predictors of sickness absence with the strongest prediction made at six-week follow-up.

If these findings are to be applied to screen patients at risk of developing persistent LBP, the next stage of research requires a validation of the results in the target population, a new sample of acute/ subacute LBP consulters in a primary care setting in New Zealand. A subsequent stage could look at the validation of the tool in different settings, such as inter-country validation; validation in a broader musculoskeletal population; or even validation in the general population.