A Multidimensional Measure of Pain Interference Reliability and Validity of the Pain Disability Assessment Scale

Objective: Measuring outcomes across multiple domains is essential for an adequate understanding of chronic pain and the effects of pain treatment. Pain interference reflects the negative effects of pain on functioning, and is recognized as a critical outcome domain. The Pain Disability Assessment Scale (PDAS) contains items that assess the negative effects of pain on broad spectrum pain interference domains. The purpose of this study was to examine the factor structure, reliability, and validity of the PDAS. Methods: One hundred sixty-four Japanese patients with chronic pain were administered the PDAS, the Brief Pain Inventory, and the Hospital Anxiety and Depression Scale. Results: The findings support a 3 factor structure of the PDAS items, as well as a high level of internal consistency of the scales created from these factors (Cronbach alpha's range: 0.87 to 0.95). Validity of the 3 scales was supported through their significant associations, in hypothesized directions, with measures of pain intensity, anxiety, depression, and another established measure of pain interference, as well as differences in PDAS scores between patients with versus without back pain. Conclusions: The PDAS may be useful when researchers or clinicians require a multidimensional measure of the effects of pain on a patient's life.