Reliability and Validity of the Evidence-Based Practice Confidence (EPIC) Scale

Introduction: The reliability, minimal detectable change (MDC), and construct validity of the evidence-based practice confidence (EPIC) scale were evaluated among physical therapists (PTs) in clinical practice. Methods: A longitudinal mail survey was conducted. Internal consistency and test-retest reliability were estimated using Cronbach's alpha and the intraclass correlation coefficient (ICC), respectively. The ICC was used to compute the MDC. We evaluated construct validity by testing hypotheses that EPIC scores would be positively associated with education level and frequency of searching, reading, and using research literature in clinical decision making. Results: At baseline, 275 PTs completed the EPIC scale and validity questionnaire and 187 completed the scale at retest (mean retest interval = 16 days). Internal consistency was 0.89 (95% confidence interval 0.86 to 0.91; N = 275). The ICC for test-retest reliability was 0.89 (95% confidence interval 0.85 to 0.91; N = 187). The MDC95 was 4.1 percentage points meaning that a change in an individual's score must be greater than 4.1 percentage points to exceed the limits of measurement error. The mean EPIC score was significantly higher among PTs holding a Masters or doctoral degree compared to those holding a bachelor's degree or diploma, and among PTs reporting searching online, reading, and using the research literature in clinical decision making 6 or more times compared to 0 to 5 times in a typical month. Discussion: Results provide evidence of excellent test-retest reliability and acceptable construct validity and minimal measurement error on repeated administration of the EPIC scale. The scale is recommended for use among PTs in clinical practice. Validation of the EPIC scale in other health professional groups is warranted.