Abstract
OBJECTIVE: To examine the predictive validity of the Subgrouping for Targeted Treatment (STarT Back) tool for classifying people with back pain into categories of low, medium, and high risk of persistent disabling back pain in U.S. primary care. DESIGN: Secondary analysis of data from participants receiving usual care in a randomized clinical trial. SETTING: Primary care clinics. PARTICIPANTS: Adults (N = 1109) ≥18 years of age with back pain. Those with specific causes of back pain (pregnancy, disc herniation, vertebral fracture, spinal stenosis) and work-related injuries were not included. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The original 9-item version of the STarT Back tool, administered at baseline, stratified patients by their risk (low, medium, high) of persistent disabling back pain (STarT Back risk group). Persistent disabling back pain was defined as Roland-Morris Disability Questionnaire scores of ≥7 at 6-month follow-up. RESULTS: The STarT Back risk group was a significant predictor of persistent disabling back pain (P<.0001) at 6-month follow-up. The proportion of individuals with persistent disabling back pain at follow-up was 22% (95% confidence interval [CI] 18-25) in the low-risk group, 62% (95% CI 57-67) in the medium-risk group, and 80% (95% CI 75-85) in the high-risk group. The relative risk of persistent disabling back pain was 2.9 (95% CI 2.4-3.5) in the medium-risk group compared to the low-risk group, and 3.7 (95% CI 3.1-4.4) in the high-risk group. CONCLUSIONS: The STarT Back risk groups successfully separated people with back pain into distinct categories of risk for persistent disabling back pain at 6-month follow-up in U.S. primary care. These results were very similar to those in the original STarT Back validation study. This validation study is a necessary first step toward identifying whether the entire STarT Back approach, including matched/targeted treatment, can be effectively used for primary care in the United States.