Construct validity of activities of daily living scale: a clue to distinguish the disabling effects of COPD and congestive heart failure.

STUDY
OBJECTIVES: To assess differences, if any, in the pattern of disability measured using basic activities of daily living (BADL) and instrumental activities of daily living (IADL) in COPD and congestive heart failure (CHF), using diabetes mellitus as a reference noncardiorespiratory disabling condition.
DESIGN: Multicenter survey.
SETTING: General medicine or geriatric wards in tertiary hospitals throughout Italy. PATIENTS: Patients admitted because of CHF (n = 432), COPD (n = 305), and diabetes mellitus (n = 534). MEASUREMENTS AND
RESULTS: Construct validity of self-reported preadmission BADL-IADL was assessed for each group by main component analysis. The three populations had a comparable average degree of dependency in BADL-IADL. In both CHF and diabetes mellitus patients, three components cumulatively explained most of variance in BADL-IADL: the BADL, 10 IADL, and 4 housework-related IADL. In COPD, a four-factor solution was generated, with factor 4 having loading with IADL items assessing mobility and outdoor moving, and factor 3 with selected IADL requiring both physical and mental capabilities such as managing money, taking medicine, and traveling. Correlates of dependency in IADL related to factor 4 in COPD were older age, cognitive impairment, widowhood, and comorbidity. Both factors 3 and 4 were associated with longer stay (factor 3: 13.9 +/- 9.5 days vs 11.5 +/- 7.6 days, p < 0.05; factor 4: 14.2 +/- 8.8 days vs 11.0 +/- 5.5 days, p < 0.05) of COPD patients (mean +/- SD).
CONCLUSION: COPD was associated with a distinctive pattern of disability expressed by loss of selected BADL-IADL but not by the crude number of lost BADL-IADL.