Real-world predictors of surgery in patients with low back pain: a CHAID analysis

Abstract

Many studies suggest that surgery for low back pain (LBP) is excessive, expensive, and often ineffective. We examine the interaction among LBP patients, of demographics, LBP diagnosis categories, co-morbidities, noninvasive therapy use, and medication use to identify diagnostic-treatment pathways that may modify likelihood of LBP surgery using CHAID (Chi-square automatic interaction detector analysis.) The 211,551 patients, ages 18-64 years, with >1 LBP diagnosis, as specified by HEDIS, between 2002 and 2006 were identified from a large administrative claims data. Patients had continuous eligibility >12 months after their index LBP diagnosis (study period) and >6 months before their index diagnosis (baseline period) and no other LBP diagnosis during the baseline period. Exploratory CHAID and logistic analyses were used to identify subgroups of the population most likely to undergo surgery. There were 4,331 patients (2.05%) who had back surgery during the study period (median: 90 days after LBP diagnosis). The likelihood of surgery increased with: age; in men; with severe LBP diagnoses such as spinal stenosis, herniated disc; chronic duration (>3 months); and prior depression. Other co-morbidities (Charlson Index, osteoporosis, asthma) decreased the likelihood of surgery. Use of opiates and corticosteroids appeared associated with increased risk and noninvasive therapies, such as chiropractic and exercise therapies, NSAIDs, and some antidepressants with lower risk. LBP chronicity and diagnostic severity, with combinations of some treatments such as opioids, corticosteroids, chiropractic therapy, NSAIDs, and antidepressants were associated with variations in subpopulation surgery risk rates from >1% to 24%. In summary, surgery risk varies with more conservative, noninvasive therapy and medication combinations, but causality cannot be inferred. Studies to model treatment selection and confounding are needed to assess these interventional prospects for surgery avoidance. (Research funding provided by Eli Lilly and Company, Indianapolis IN.)