Predicting 7-day and 3-month functional outcomes after an ED visit for acute nontraumatic low back pain

Recent work has shown that two-thirds of patients report functional disability 1 week after an emergency department (ED) visit for nontraumatic musculoskeletal low back pain (LBP). Nearly half of these patients report functional disability 3 months later. Identifying high-risk predictors of functional disability at each of these 2 time points will allow emergency clinicians to provide individual patients with an evidence-based understanding of their risk of protracted symptoms.

The aim of the present study was to determine whether 5 high-risk features previously identified in various primary care settings predict poor functional outcomes among patients in the ED. The hypothesized predictors are as follows: LBP-related functional disability at baseline, radicular signs, depression, a work-related injury, or a history of chronic or recurrent LBP before the index episode.

We conducted a prospective observational cohort study of patients in the ED with a chief complaint of nontraumatic LBP, which the ED attending physician classified as musculoskeletal. We interviewed patients in the ED before discharge and performed a baseline assessment of functional disability using the 24-item Roland-Morris questionnaire. We also trichotomized the patient's baseline history of LBP into chronic (defined as 30 straight days with continuous LBP or a history of acute exacerbations more frequently than once per week); episodic (acute exacerbations more frequently than once per year but less frequently than once per week), or rarely/never (less frequently than once per year or no history of LBP). We performed telephone follow-up 1 week and 3 months after ED discharge using a scripted closed-question data collection instrument. The primary outcome was any functional limitation attributable to LBP at 1 week and 3 months, defined as a score greater than zero on the Roland-Morris questionnaire. We used logistic regression, adjusted for age, sex, and educational level, to assess the independent association between functional disability and each of the 5 hypothesized predictors listed above.

We approached 894 patients for participation and included 556. We obtained follow-up on 97% and 92% of our sample at 1 week and 3 months, respectively. Two of the 5 hypothesized variables predicted functional disability at both time points: higher baseline Roland-Morris score (odds ratio [OR], 4.3; 95% confidence interval [CI], 2.6-6.9) and chronic LBP (OR, 2.3; 95% CI, 1.1-4.8) were associated with 7-day functional disability. These same 2 variables predicted functional disability 3 months after ED discharge-higher baseline Roland-Morris score (OR, 2.3; 95% CI, 1.4-3.9) and chronic LBP (OR, 2.8; 95% CI, 1.5-5.2). The remaining 3 hypothesized predictors (depression, radicular signs, and on-the-job injury) did not predict functional outcome at either time point.

Patients in the ED with worse baseline functional impairment and a history of chronic LBP are 2 to 4 times most likely to have poor short- and longer-term outcomes.