Can Proxy Ratings Supplement Patient Report to Assess Functional Domains Among Hospitalized Patients?

Objective: To (1) characterize the agreement between patient and proxy responses on a multidimensional computerized adaptive testing measure of function, and to (2) determine whether patient, proxy, or multidimensional computerized adaptive testing score characteristics identify when a proxy report can be used as a substitute for patient report in clinical decision making. Design: A psychometric study of the Functional Assessment in Acute Care Multidimensional Computerized Adaptive Testing (FAMCAT) and its 3 scales (Applied Cognition, Daily Activity, and Basic Mobility). Setting: An upper midwestern quaternary academic medical center Participants: A total of 300 pairs of patients (average age 60.9 years; range, 19-89) hospitalized on general medical services or readmitted to surgical services for postoperative complications and their proxies (average age 60.5 years; range, 20-88). Intervention: Not applicable. Main Outcome Measures: There were 3 outcomes: (1) agreement between patient and proxy scores on the FAMCAT domains, as well as age and sex, analyzed with univariate and multivariate analysis of variance (MANOVA); (2) associations of patient-proxy relationship and FAMCAT score characteristics with patient-proxy score agreement; and (3) presence of psychometrically significant intra-dyad differences in FAMCAT scores. Results: The results of the MANOVA and follow-up ANOVAs indicated that there were no statistically significant differences in FAMCAT scale scores between patient and proxy estimates for either the Daily Activity or Basic Mobility scales. There were significant differences for the Applied Cognition scale (P<.005) between mean patient and proxy scores, with proxies rating patients as functioning at a higher level (mean=0.42) than patients did themselves (mean=0.00). However, psychometrically significant intra-dyadic Applied Cognition score differences occurred in only 14% of dyads, compared with 25% in the other 2 scales. Sex and age were associated with patient-proxy agreement, but the patterns were not sufficiently consistent to permit generalizations regarding the likely validity of a proxy's scores. Conclusions: Patient and proxy FAMCAT Daily Activity and Basic Mobility scores did not differ significantly, and proxy reporting offers a creditable surrogate for patient report on these domains. Low rates of psychometrically significant intra-dyadic score differences suggest that proxy report may serve as a low-resolution screen for functional deficits in all FAMCAT domains. Approximately half the proxies provided multi-domain profile ratings on the 3 scales that did not differ significantly from these of the associated patients, but more research is needed to identify situations in which proxy profiles could be used in place of those provided by patients.