Psychometric evaluation of the German version of the patient activation measure (PAM13)

BACKGROUND: The Patient Activation Measure (PAM) consists of 13 items and assesses patient (or consumer) self-reported knowledge, skills, and confidence for self-management of one's health or chronic condition. The aim of this study was to translate the original American version of the PAM13 into German and to test the psychometric properties of the German version in an elderly, multimorbid population with various chronic conditions.

METHODS: Translation was performed by a standardized forward-backward translation process. The PAM13 was sent to 9.075 participants enrolled in a randomized controlled study. 4.306 participants responded to the questionnaire. Descriptive and reliability analyses were carried out. To examine scale properties, Andrich's Rasch Rating Scale Model was fitted.

RESULTS: The internal consistency is good (α = 0.88) and the item-rest-correlations were found as strong to moderate. The unidimensionality of the construct was confirmed, with a variance explanation of 40.9% and good model-fits for the Rasch model. However, the lowest response options were very rarely used across all items (below 5%) and ranking order of items according to their difficulty was substantially different from that of the American version. Differential item functioning (DIF) was found in subgroups (sex, age, health status), but differences were small.

CONCLUSION: The German version of the PAM13 showed acceptable reliability and the model-fit statistics confirmed the Rasch model. The different ranking order of the items and the unfair distribution of the response options suggest further research on validation and revision of the construct.