Pain One Week After an Emergency Department Visit for Acute Low Back Pain Is Associated With Poor Three-month Outcomes

Background: Low back pain (LBP) is responsible for more than 2.5 million visits to U.S. emergency departments (EDs) annually. Nearly 30% of patients who present to an ED with acute LBP report functional impairment or pain 3 months later. These patients are at risk of chronic LBP, a highly debilitating condition. In this study, we assessed whether three variables assessable shortly after symptom onset could independently predict poor 3-month outcomes among LBP patients who present to an ED. Methods: This was a planned analysis of data from two randomized comparative effectiveness studies of patients with acute, nontraumatic, nonradicular LBP. Patients were enrolled during an ED visit, contacted by telephone 1 week after the ED visit, and then followed up by telephone 3 months later. The coprimary 3-month outcomes were LBP-related functional impairment and persistent moderate or severe LBP. Two of the three hypothesized predictor variables were assessed during the index visit: 1) the STarT Back Screening Tool score, a nine-item, multidimensional tool validated and widely used in the outpatient setting, and 2) the patient's own anticipated duration of LBP. The third hypothesized predictor was presence of pain assessed by phone 1 week after the ED visit. We then determined whether these three predictor variables were independently associated with poor outcomes at 3 months, after controlling for medication received, age, and sex. Results: A total of 354 patients were enrolled. Of these, 309 (87%) provided 3-month impairment data and 311 (88%) provided 3-month pain data. At 3 months, 122 of 309 (39%) patients reported functional impairment and 51 of 311(16%) patients reported moderate or severe LBP. Among the three hypothesized predictor variables, 58 of 352 (16%) patients with available data reported a moderate or high STarT Back Screening Tool score, 35 of 321 (11%) patients with available data reported anticipated duration of LBP > 1 week, and 235 of 346 (68%) patients reported pain at 1-week telephone follow-up. After age, sex, and medication received were controlled for in a multivariable logistic regression model, only pain at 1 week was independently associated with 3-month impairment (odds ratio [OR] = 2.42, 95% CI = 1.39–4.22) and 3-month moderate or severe pain (OR = 3.83, 95% CI = 1.53–9.58). Conclusions: More than one-third of patients reported functional impairment 3 months after an ED visit for acute, nontraumatic, nonradicular LBP. Moderate or severe LBP was less common, reported in about half as many patients (16%). Of the three hypothesized predictor variables, only persistent pain at 1 week was independently associated with poor outcomes at 3 months. Despite its important role in the outpatient setting, the STarT Back Tool was not associated with poor outcomes in this ED cohort.