Functional status before hospitalization in acutely ill older adults: validity and clinical importance of retrospective reports.

OBJECTIVES: Retrospective reports of patients' functional status before hospital admission are often used in longitudinal studies and by clinicians caring for hospitalized patients. However, the validity of these reports has not been established. Our aim was to examine the validity of retrospective reports by testing hypotheses about the relationships these measures would have with other clinical measures if they were valid.
DESIGN: A prospective cohort study. PARTICIPANTS AND
SETTING: A total of 2877 older patients (mean age 81, 36% women) hospitalized on the general medical service at two hospitals. For 1953 of the subjects, the patient was the primary respondent, whereas for 924 subjects, a surrogate was the primary respondent. MEASUREMENTS: Shortly after hospital admission, patients or surrogates reported whether the patient was independent in each of five activities of daily living (ADLs) on admission and at baseline 2 weeks before admission. Outcome measures included reported independence in each ADL 3 months after the hospitalization and survival to 1 year.
RESULTS: Patients' retrospective reports of their ADL function 2 weeks before admission had a clinically plausible relationship with ADL function at the time of admission, in that patients independent in an ADL on admission rarely reported they were dependent in that ADL 2 weeks before admission (range 2-6%). Surrogates were somewhat more likely than patients to report that patients independent on admission were dependent 2 weeks before admission (range 5-14%). Retrospective reports of prehospitalization ADL function demonstrated strong evidence of predictive validity for both patients' and surrogates' reports. For example, among patients dependent in bathing on admission, patients who were reported as independent 2 weeks before admission were much more likely than those reported as dependent 2 weeks before admission to be independent 3 months after hospitalization (68% vs 20%, P < .001 for patient respondents; 30% vs 5%, P < .001 for surrogate respondents). Similarly, among patients dependent in bathing on hospital admission, survival 1 year after hospitalization was much higher in patients who were independent in bathing 2 weeks before admission than patients who were dependent 2 weeks before admission (76% vs 59%, P < .001 for patient respondents; 60% vs 45%, P < .001 for surrogate respondents). Results were similar for each of the other four ADLs. In a logistic regression model controlling for the number of ADLs reported as dependent on admission, the number of ADLs reported as dependent 2 weeks before admission was significantly associated with 1-year mortality among both patient (odds ratio (OR) = 1.39 per dependent ADL, 95% confidence interval (CI) - 1.26-1.54) and surrogate (OR = 1.14, 95% CI = 1.06-1.24) respondents.
CONCLUSIONS: Hospitalized patients' assessments of their ability to perform ADLs before their hospitalization have evidence of face and predictive validity. These measures are strong predictors of important health outcomes such as functioning and survival. In particular, among patients dependent in ADL function on hospital admission, these results highlight the prognostic importance of inquiring about the patient's functional status before the onset of the acute illness.