Use of Proxy Respondents and Accuracy of Minimum Data Set Assessments of Activities of Daily Living

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Abstract
Background. Although the Minimum Data Set (MDS) presents a wide range of opportunities for policy makers and practitioners interested in outcomes of nursing home care for frail elderly persons, researchers have debated the validity and reliability of measurements in the MDS from the outset. To investigate this issue, the authors studied the accuracy of functional assessments by comparing the MDS and interview data collected in two evaluation studies. Methods. Activities of daily living (ADL) assessment data from 3385 nursing home residents were collected from interviews with nursing home residents (n = 1200), family members (n = 1070), and nursing home staff (n = 1115). The MDS data for these nursing home residents were obtained and matched with the interview data. The agreement in ADL assessments between interview data and the MDS was assessed using Kappa statistics and multinomial logit regression for each of the three data sources. Results. The agreement on ADL assessments between MDS and interview data was low to moderate (Kappa = 0.25 to 0.52), regardless of the sources of data. Interview data from staff and family proxies agreed to a greater degree with the MDS than did data collected from nursing home residents. The MDS reported fewer ADL difficulties than did staff proxies and more ADL difficulties than did nursing home residents. These findings held even after adjustment for other confounding factors using multinomial logit regression. Conclusions. The substantial discrepancy between MDS and interview data can be attributed to both bias and error. The ADL assessments based on residents' and family or staff reports differ, but the size of these differences depends on the proxy type and the method of data collection.