Factor structure and psychometric properties of the Pain Anxiety Symptoms Scale-20 in a community physiotherapy clinic sample.

The PASS-20 was developed to assess pain-related anxiety among a variety of pain populations. This measure was constructed by extracting 20 items from its 40-item parent measure (PASS). Initial studies of the PASS-20 suggest that the psychometric properties have been preserved. The purpose of the present study extended this research and explored the factor structure of the PASS-20, and its reliability and validity in a sample of pain patients receiving treatment in a community physiotherapy clinic. Patients with current pain (n = 201) were asked to complete a battery of self-report measures related to the experience of pain on two separate occasions (3-month interval). Results of principal components analyses suggested that a 4-factor solution representing fear of pain, escape-avoidance, physiological symptoms, and cognitive symptoms of anxiety provided the best fit to these data. Results also showed that the total and subscale scores of the PASS-20 have good reliability (internal consistency, test-retest) and validity (construct) correlating greater with other conceptually similar measures than distinct constructs. These results suggest that this measure has good utility for both clinical and research applications. Directions for future evaluation are also discussed.