Background: The PASS-20 (McCracken and Dhingra, Pain Res Manag 7:45-50, 2002) is a shortened version of the Pain Anxiety Symptoms Scale (PASS), a self-report measure of pain anxiety. The PASS-20 demonstrates good psychometric characteristics but has not yet been validated in a German population.
Purpose: The aims of the present study were to (1) examine the factor structure and psychometric characteristics of the German PASS-20; (2) investigate its construct validity with respect to depression, fear-avoidance, and endurance; and (3) determine its criterion-related validity with a special emphasis on pain, disability, and quality of life.
Method: A principal component analysis was performed on a sample (N = 195) of patients with acute, subacute, and chronic low back pain. Reliability was examined with Cronbach's α. Validity was assessed by correlating the PASS-20 to measures of depression, anxiety, disability, quality of life, and avoidance-endurance-related behavioral pain responses.
Results: The original four-factor structure proposed for the PASS-20 was replicated using the original subscale labels. The reliability of the total score and the subscales was satisfactory to excellent, and both convergent and divergent validity were moderate to high in the expected directions, showing positive correlations with anxiety, fear, depression, and fear-avoidance and negative correlations with endurance and quality of life. The PASS-20 showed unique predictive ability and advantages over the Tampa Scale of Kinesiophobia.
Conclusions: The results for the German PASS-20 support the original factor structure and provide evidence of satisfactory psychometric characteristics and usefulness in patients with low back pain.