Validation of the Patient Activation Measure (PAM-13) among adults with cardiac conditions in Singapore

Purpose The Patient Activation Measure (PAM-13) measures patients' knowledge, skill, and confidence in chronic condition self-management. The purpose of this study was to assess the validity of PAM-13 (English version) among English-speaking adults with cardiac conditions in Singapore. Methods A cross-sectional study was conducted in a convenient sample of 270 heart clinic patients. Using the unitary concept of validity, evidence of (1) internal structure via data quality, unidimensionality, differential item functioning, and internal consistency, (2) response process through item difficulty and item fit using Rasch modeling, and (3) relationship to other variables via correlations with depression and self-efficacy were examined. Results The item response was high with only one missing answer. All items had a small floor effect, but nine out of 13 items had a ceiling effect larger than 15 %. Cronbach's α was 0.86, and average inter-item correlations was 0.324. Results suggested unidimensionality; however, differences in item difficulty ranking were found. A low, negative correlation was found with depression, while a moderate, positive correlation was found with self-efficacy. Conclusion Evidence in all three areas of validity were mixed. Caution should be exercised when using categorical activation "level" to inform clinical decisions.