Factor Structure of the Pain Disability Index in Workers’ Compensation Claimants With Low Back Injuries

Abstract

Tait RC, Chibnall JT. Factor structure of the Pain Disability Index in workers’ compensation claimants with low back injuries. Arch Phys Med Rehabil 2005;86:1141–6. Objective To examine the factor structure of a telephone-administered Pain Disability Index (PDI) and the effects of race and sex on the PDI. Design Computer-assisted telephone interviews of a cohort with occupational low back injuries. Setting General community. Participants Missouri workers’ compensation claimants (N=1329) with low back injuries. Interventions Not applicable. Main Outcome Measures PDI, levels of pain severity, Social Security Disability Insurance status, and the Fear-Avoidance Behavior Questionnaire. Results Results for the total sample and by race/sex group indicated support for a 2-factor model of the PDI corresponding to voluntary activities (eg, social, occupational, recreational) and obligatory activities (eg, activities of daily living, eating, sleeping). Additional psychometric analyses of the voluntary and obligatory subscales indicated adequate reliability and construct validity overall and in each of the race/sex groups. African Americans reported more pain-related disability on both subscales than whites. Women reported more disability on the voluntary subscale than men. Conclusions The results support use of the PDI as a bidimensional measure of pain-related disability, with strong psychometric properties. They also support its administration by telephone.