Clinical Decision Rule for Primary Care Patient with Acute Low Back Pain at Risk of Developing Chronic Pain
Wolf E. Mehling, MD, Mark H. Ebell, MD, MS, Andrew L. Avins, MD, MPH, Frederick M. Hecht, MD
Department of Family Medicine,
University of California-San Francisco,
1545 Divisadero St,
San Francisco, CA 94115, USA
BACKGROUND CONTEXT: Primary care clinicians need to identify candidates for early interventions to prevent patients with acute pain from developing chronic pain.
PURPOSE: We conducted a 2-year prospective cohort study of risk factors for the progression to chronic pain and developed and internally validated a clinical decision rule (CDR) that stratifies patients into low-, medium-, and high-risk groups for chronic pain.
STUDY DESIGN/SETTING: This is a prospective cohort study in primary care.
PATIENT SAMPLE: Patients with acute low back pain (LBP, ≤30 days duration) were included.
OUTCOME MEASURES: Outcome measures were self-reported perceived nonrecovery and chronic pain.
METHODS: Patients were surveyed at baseline, 6 months, and 2 years. We conducted bivariate and multivariate regression analyses of demographic, clinical, and psychosocial variables for chronic pain outcomes, developed a CDR, and assessed its performance by calculating the bootstrapped areas under the receiver-operating characteristic curve (AUC) and likelihood ratios.
RESULTS: Six hundred five patients enrolled: 13% had chronic pain at 6 months and 19% at 2 years. An eight-item CDR was most parsimonious for classifying patients into three risk levels. Bootstrapped AUC was 0.76 (0.70-0.82) for the 6-month CDR. Each 10-point score increase (60-point range) was associated with an odds ratio of 11.1 (10.8-11.4) for developing chronic pain. Using a less than 5% probability of chronic pain as the cutoff for low risk and a greater than 40% probability for high risk, likelihood ratios were 0.26 (0.14-0.48) and 4.4 (3.0-6.3) for these groups, respectively.
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CONCLUSIONS: A CDR was developed that may help primary care clinicians classify patients with strictly defined acute LBP into low-, moderate-, and high-risk groups for developing chronic pain and performed acceptably in 1,000 bootstrapped replications. Validation in a separate sample is needed.
KEYWORDS: Acute pain; Chronic pain; Clinical decision rule; Low back pain; Prediction; Primary care
From The FULL TEXT Article
Although most patients presenting with an episode of acute low back pain (LBP) in primary care will recover in six to eight weeks with or without medical intervention, [1, 2] those who subsequently develop chronic pain suffer considerably,  often are difficult to treat, and account for most LBP-related health expenses.  Primary care clinicians need decision support to identify candidates for early interventions for secondary prevention of chronic pain. Previous studies have identified risk factors for chronic pain, and have attempted to develop clinical decision rules for the primary care setting. [5, 6] The most important are the STarT-Back developed in the UK [7, 8] and the Chronic Pain Risk Screener (CPRS) developed in the US. 
The STarT-BACK and several instruments developed in Europe (Örebro Musculoskeletal Pain Screening Questionnaire (ÖMPSQ) [10, 11], Kiel Pain Inventory and Avoidance-Endurance Questionnaire, [12, 13] and Heidelberger Kurz-Fragebogen (HKF) ) have not been evaluated in the US. Other limitations of the latter instruments are that they were not developed or validated in primary care patients and used delayed return-to-work as chronic pain outcomes, which only captures a subset of patients taking sick leave.
Both the STarT-BACK and CPRS have been well validated in patients shortly following an index visit at a primary care office.  However, these index visit patients included patients with a wide range of LBP duration; less than half suffered from acute LBP. Because patients who suffer LBP for more than 3 months already have a much worse prognosis, instruments that work for this population may not perform as well in patients with acute LBP. Hence, clinicians need a tool that only addresses the prognosis of patients with truly acute LBP. 
We therefore conducted a prospective cohort study to investigate the prognosis of patients with strictly defined acute LBP , and whether we can identify early risk factors that can help primary care clinicians determine a more accurate prognosis. If available such risk stratification would be feasible for primary care clinics and could potentially support physicians in treatment allocation decisions. We included questionnaire items representative of all risk factors known at the time of the cohort’s inception and set out to develop a novel clinical decision rule (CDR).