Development of a Frailty Ladder Using Rasch Analysis: If the Shoe Fits
Keywords:frailty, Rasch analysis, measurement theory, performance tests, self-reported outcomes
The current measurement approach to frailty is to create an index of frailty status, rather than measure it. The purpose of this study is to test the extent to which a set of items identified within the frailty concept fit a hierarchical linear model (e.g., Rasch model) and form a true measure reflective of the frailty construct.
A sample was assembled from three sources: community organization for at-risk seniors (n=141); colorectal surgery group assessed post-surgery (n=47); and hip fracture assessed post-rehabilitation (n=46). The 234 individuals (age 57 to 97) contributed 348 measurements. The frailty construct was defined according to the named domains within commonly used frailty indices, and items drawn to reflect the frailty came from self-report measures. Performance tests were tested for the extent to which they fit the Rasch model.
Of the 68 items, 29 fit the Rasch model: 19 self-report items on physical function and 10 performance tests, including one for cognition; patient reports of pain, fatigue, mood, and health did not fit; nor did body mass index (BMI) nor any item representing participation.
Items that are typically identified as reflecting the frailty concept fit the Rasch model. The Frailty Ladder would be an efficient and statistically robust way of combining results of different tests into one outcome measure. It would also be a way of identifying which outcomes to target in a personalized intervention. The rungs of the ladder, the hierarchy, could be used to guide treatment goals.
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