Comparative evaluation of the psychometric properties of orthopedic scales for low back pain
Objective: To evaluate the reliability, response capacity and validity of four scales for low back pain and correlate these scales with each other and the Self-Administered Comorbidity Questionnaire (SACQ). Methods: We evaluated the psychometric properties of four previously selected scales for low back pain: the Roland-Morris Disability Questionnaire (RMDQ), the Quebec Back Pain Questionnaire (QBPDS), the Waddell Disability Index (WDI) and the Back Pain Functional Scale (BPFS) and Self-Administered Comorbidity Questionnaire (SACQ) comorbidity scale. Exploratory and confirmatory factor analyses were conducted. Reliability and internal consistency were measured by Cronbach’s alpha. Validity was measured through correlation of the scales with the Self-Administered Comorbidity Questionnaire comorbidity scale and an analysis of the structural equations between them. Results: The scales showed adequate indicators based on the factor structure and showed Kaiser-Meyer-Olkin values above 0.90. After the exploratory factor analysis, all scales showed fit indicators suited to a factor model, following the same pattern as the original validations. Similarly, they showed good internal consistency (Cronbach’s alpha greater than .78). The only scale that showed factor loadings suggesting the exclusion of any item was the Roland-Morris. In terms of validity, the scales showed positive correlation coefficients similar to the Self-Administered Comorbidity Questionnaire and between them. Conclusion: Regarding the scales evaluated, they showed similar indications of reliability and internal consistency, such that we did not find sufficient evidence to indicate one scale over another.
