Psychometric evaluation of the Pain Anxiety Symptoms Scale (PASS) in chronic pain patients.

This study examined psychometric properties of the Pain Anxiety Symptoms Scale (PASS), a measure of pain-related fear. A recently developed shortened version of the PASS, the PASS-20, was also investigated. Previously reported factor structures of the PASS were tested by means of confirmatory factor analysis. Results indicated that all models fitted adequately but that a five-factor solution fitted slightly better compared to the other models tested. The four-factor solution of the PASS-20 was tested by means of confirmatory factor analysis and results indicated adequate fit. Moreover, the four-factor solution of the PASS-20 was invariant among fibromyalgia and low-back pain patients. Convergent validity of the original PASS and the PASS-20 was good and internal consistency reliability adequate to excellent. The suitability of the original PASS and the PASS-20 are discussed and directions for future research are provided.