The Pain Disability Index: factor structure and normative data.

The factor structure and normative data for the Pain Disability Index (PDI) were examined in a large (N = 1,059) sample of chronic pain patients. The results support a one-factor solution for the PDI. Analyses of normative data indicated very small effects associated with gender, age, and pain duration. Relatively larger effects were associated with compensation status, litigation status, and circumstances of pain onset. Working patients reported less disability than their nonworking counterparts, litigating patients reported more disability than nonlitigants, and patients injured at work reported higher levels of disability than those with pain origins unrelated to work. The results reflect the disability level of patients referred to a hospital-based pain management program and may be useful as a reference point when comparing disability levels of other patient groups or research samples.