ELderly Functional Index (ELFI): Validation of a self-reported measure of functional status in cancer patients.

Abstract

e19126 Background: Functional assessment of oncology patients can be challenging and is often not performed, or is undertaken by the clinician with minimal direct input from the patient. The ELderly Functional Index (ELFI) is a 12-item composite measure of self-reported functioning in cancer patients. ELFI is derived from four scales from the European Organisation for Research and Treatment of Cancer (EORTC) health-related quality of life (HRQOL) suite: Physical, Role and Social Functioning, and Mobility. This study validated ELFI in patients attending oncology clinics. Methods: For evaluation of validity and internal consistency, 621 cancer patients (31% aged >70 years) fully self-completed the ELFI, cognitive functioning (CF) and emotional functioning (EF) scales of the EORTC QLQ-C30, ECOG-performance status (ECOG-PS), instrumental activities of daily living (IADL) and Clinical Frailty Scale (CFS). For evaluation of test-retest reliability, 278 participants self-completed ELFI, CF, EF, ECOG-PS and Global Rating of Change one week later. Results: ELFI demonstrated excellent internal consistency (Cronbach alpha 0.93, p< 0.001) and test-retest reliability (intraclass correlation coefficient 0.90, p< 0.001). Hypotheses regarding convergent and discriminant validity were confirmed (multitrait-scaling). ELFI was better than its component scales and other function measures at differentiating between participants with different function and frailty scores (known-groups validity, Table). Exploratory factor analysis provided empirical support to the structural validity of ELFI. Strong correlation was observed between ELFI, function and frailty scores. Conclusions: ELFI is a validated patient-reported outcome measure of functional status. ELFI captures broader dimensions of functioning compared to ECOG-PS or IADL. As a composite measure, ELFI has enhanced statistical efficiency, reducing the sample size required to detect a given effect. ELFI could be used as a clinical trial endpoint to assess the functional domains of HRQOL. [Table: see text]