Development and COSMIN-based psychometric evaluation of the activities of daily living questionnaire for elderly iranian patients with chronic obstructive pulmonary disease (ADLEC): a sequential exploratory mixed-methods study using hybrid concept analysis

Abstract

Activities of daily living (ADL) are substantially compromised in elderly patients with chronic obstructive pulmonary disease (COPD) owing to exertional dyspnoea and fatigue. Generic instruments fail to capture disease-specific functional limitations, whereas existing disease-specific tools lack conceptual grounding and cultural sensitivity. The present study aimed to clarify the concept of ADL among elderly Iranian patients with COPD and to develop and psychometrically validate a culturally sensitive, disease-specific instrument—the Activities of Daily Living in Elderly COPD Patients (ADLEC) questionnaire—in accordance with the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) framework. A sequential exploratory mixed-methods design was utilised. In Phase 1, a hybrid concept analysis encompassing three stages (theoretical, fieldwork, and final analytical) was conducted with 15 elderly patients to delineate the conceptual attributes of ADL. In Phase 2, Waltz’s four-stage instrument development framework was employed to construct the items. Psychometric properties were evaluated across seven independent, non-overlapping samples (total N = 770), all recruited at a single national referral hospital for pulmonary diseases in Tehran, Iran. Exploratory factor analysis (EFA; n = 300) and confirmatory factor analysis (CFA; n = 250) were performed on independent samples. Reliability and agreement ( n = 30), construct validity via hypothesis testing ( n = 120), known-groups validity, longitudinal responsiveness ( n = 45), and gender-based measurement invariance ( N = 550) were systematically evaluated. The hybrid concept analysis identified three core attributes: the complexity and multifactorial nature of activity, dyspnoea and its modulators, and striving for independent living. The ADLEC was constructed as a 21-item questionnaire with a three-factor structure (Self-Care, Daily Physical Activity, and Energy Preservation & Social Participation) explaining 64.8% of the total variance. Confirmatory factor analysis indicated an adequate model fit (comparative fit index = 0.943, Tucker–Lewis index = 0.936, root mean square error of approximation = 0.069, standardised root mean square residual = 0.058). Latent-level construct validity was supported by the average variance extracted (0.60–0.76) and the heterotrait–monotrait ratio (< 0.85). The ADLEC correlated substantially with the COPD Assessment Test ( r = − 0.74), the St. George’s Respiratory Questionnaire ( r = − 0.71), and the six-minute walk test (r = + 0.62), and demonstrated large known-groups discrimination across Global Initiative for Chronic Obstructive Lung Disease severity stages (η² = 0.383). Overall scale reliability was excellent (Cronbach’s α = 0.938, McDonald’s ω = 0.93, intraclass correlation coefficient (2,1) = 0.920). The minimal detectable change at the 95% confidence level was 10.13 points and the minimal important change was 9.1 points. Longitudinal responsiveness was substantial (Cohen’s d = 0.69, standardised response mean = 0.80, area under the curve = 0.899). Strict measurement invariance across gender groups was confirmed (change in comparative fit index, ΔCFI = − 0.008). The 21-item ADLEC is a psychometrically sound, reliable, responsive, and culturally sensitive instrument. It is clinically feasible (mean completion time: 9.4 min) and may be used with a simple unweighted scoring approach to monitor functional status and evaluate pulmonary rehabilitation outcomes in elderly patients with COPD. Because all samples were drawn from a single referral hospital, multi-centre validation is warranted to confirm generalizability to other healthcare settings.