The Penn Shoulder Score: Reliability and validity

Study Design: Psychometric evaluation of a cross-sectional survey. Objectives: The purpose of this study was to examine the psychometric properties of reliability and validity of the Penn Shoulder Score (PSS). Background: Shoulder outcome measures are used to assess patient self-report levels of pain, satisfaction, and function. The PSS is a 100-point shoulder-specific self-report questionnaire consisting of 3 subscales of pain, satisfaction, and function. This scale has been utilized in the literature. However, the measurement properties of reliability and validity, including responsiveness, of the PSS subscales and overall scale need to be established. Methods and Measures: Patients (n = 40) with shoulder disorders undergoing a course of outpatient physical therapy completed the PSS at initial visit and again within 72 hours to assess test-retest reliability. The Constant Shoulder Score (CSS) and the American Shoulder and Elbow Surgeons Shoulder Score (ASES) were also completed at the initial visit and compared to the PSS to assess convergent construct validity. A separate cohort of patients (n = 109) completed the PSS at initial visit and 4 weeks later. These scores were used to assess internal consistency and responsiveness. Results: Reliability analysis revealed a test-retest IC2,1 of 0.94 (95% CI, 0.89-0.97). Internal consistency analysis revealed a Cronbach alpha of 0.93. The standard error of measurement (SEM) was 8.5 scale points (based on a 90% CI) and the minimal detectable change (MDC) was 12.1 scale points (based on a 90% CI). The minimal clinically important difference (MCID) for improvement was 11.4 points. Pearson product moment correlation coefficients between the PSS and the CSS and ASES were 0.85 and 0.87, respectively. Responsiveness analysis revealed an effect size of 1.01 and a standardized response mean of 1.27. Conclusions: This study has demonstrated that the PSS is a reliable and valid measure for reporting outcome of patients with various shoulder disorders.