Performance of the Medicare Consumer Assessment of Health Care Providers and Systems (CAHPS) Physical Functioning Items.

BACKGROUND Physical functioning is an important health domain for adults. OBJECTIVE Evaluate physical functioning items in Medicare beneficiaries. RESEARCH DESIGN Survey data from the 2010 Consumer Assessment of Healthcare Providers and Systems Medicare survey. SUBJECTS The 366,701 respondents were 58% female; 38% were 75 or older; 57% had high school education or less. MEASURES Walking, getting in or out of chairs, bathing, dressing, toileting, and eating assessed with 3 response choices: unable to do, have difficulty, do not have difficulty. RESULTS Pearson correlations among the 6 items ranged from 0.515 to 0.835 (coefficient α=0.92). A single factor categorical factor analytic model fit the data well (comparative fit index=0.998; root mean square error of approximation=0.083). The item with the highest percentage of respondents reporting no difficulty was eating, followed by toileting, dressing, bathing, getting in and out of a chair, and walking. Threshold parameters from an item response theory-graded response model ranged from -1.983 (between unable to do and have difficulty eating) to -0.551 (between have difficulty and no difficulty walking). Item discrimination parameters ranged from 4.632 (walking) to 8.228 (dressing). IRT-scored physical functioning scores correlated with self-rated general health (r=0.389, n=344,843, P<0.0001) mental health (r=0.296, n=351,254, P<0.0001) and number of chronic conditions (r=-0.229, n=284,507, P<0.0001). CONCLUSIONS The physical functioning items target relatively easy activities, providing information for a minority of people in the sample with the lowest levels of physical functioning. Items representing higher levels of physical functioning are needed for the majority of the Medicare beneficiaries.