Centralization: prevalence and effect on treatment outcomes using a standardized operational definition and measurement method.

STUDY DESIGN: Retrospective, observational cohort design. OBJECTIVES: Purpose 1 was to determine the association between age, symptom chronicity, and prevalence of centralization in a sample of patients with nonserious cervical or lumbar spinal syndromes referred to a hospital-based outpatient rehabilitation clinic. Purpose 2 was to examine if classifying these patients at intake to centralization or noncentralization predicts functional status, pain intensity, and number of treatment visits at discharge from rehabilitation. Purpose 3 was to compare clinically meaningful changes in functional status and pain intensity between patients subgrouped by centralization and noncentralization. BACKGROUND: Variations in operational definitions and measurements used to identify centralization affect patient classification, contribute to variation in reported prevalence rates, and influence treatment strategy and outcome interpretation. Investigating a standardized operational definition and measurement method for centralization may reduce practice and outcomes variation. METHODS AND MEASURES: Adults (n=418) with cervical or low back syndromes (mean +/- SD age, 58 +/- 17 years; range, 19-91 years; 33% male; 76% lumbar symptoms; 53% chronic symptoms) were assessed. Therapists classified patients using a standardized operational definition and method for centralization during initial evaluation. Prevalence rates were calculated for centralization by age and acuity. Multivariate models were used to assess discharge functional status, pain intensity, and visits while controlling important variables. Percentage of patients subgrouped by centralization and noncentralization achieving minimal clinically important differences (MCID) in functional status and pain intensity was assessed. RESULTS: Overall prevalence rate for centralization was 17%, but increased for patients who were younger and reported acute symptoms regardless of body part. For patients with lumbar syndromes, noncentralization was associated with lower discharge functional status and more pain, but not associated with number of visits compared to patients classified as centralization. For patients with cervical syndromes, noncentralization was associated with more pain but not associated with functional status or number of visits compared to patients classified as centralization. Pain pattern classification affected percentage of patients with lumbar and cervical impairment achieving MCID. CONCLUSION: Results supported the clinical use of a standardized definition of centralization to facilitate patient classification and management and interpretation of outcomes.