Rasch analysis of the Katz index of independence in activities of daily living in senior citizens from Antioquia, Colombia

• Published in: Revista de la Facultad Nacional de Salud Pública Vol. 37; no. 2; pp. 89 - 95
• Main Authors: Rojas-Gualdrón, Diego Fernando, Ayala-Hernández, Jessica María, Cardona-Arango, Doris, Segura-Cardona, Angela María, Garzón-Duque, María Osley
• Format: Journal Article
• Language: English; Spanish
• Published: Medellín Universidad de Antioquía 01.05.2019; Universidad de Antioquia
• Subjects: 80 and over; Activities of daily living; Aged; Data analysis; Decision making; fisioterapía; Older people; Population studies; psicometría; PUBLIC, ENVIRONMENTAL & OCCUPATIONAL HEALTH; Rasch model; Reliability analysis; salud pública; Statistical analysis; Subpopulations; Validation studies; Colombia; 80 and over; atividades de vida diária; Activities of daily living; estudios de validación; idoso; pessoa de 80 anos ou mais; actividades de la vida diaria; Aged; anciano; persona de 80 años o más; Validation studies; estudos de validação
• ISSN: 0120-386X; 2256-3334; 0120-386X
• DOI: 10.17533/udea.rfnsp.v37n2a10

Improving Katz index interpretability contributes to a better understanding of its results facilitating decision making and intervention planning.Objective: To evaluate the validity of the Katz geriatric scale in senior citizens from a Rasch model perspective.Methodology: Secondary data analysis of a population-based, cross-sectional study of health status in 4,023 senior citizens conducted in Antioquia, Colombia, in 2012. Item fit, differential item functioning, unidimensionality, reliability and item-person map analyses were performed.Results: All items adjusted to the model. Transferring and Continence showed high differential item functioning with a considerable, but statistically non-significant impact on the overall estimation. Person and Item reliability were 0.80 and 0.90 respectively. The Rasch measurement explained 61.6% of variance.Conclusion: A unidimensional interval level measure can be obtained from the Katz instrument. It is important to do more research on differential functioning of Katz’s items in a way in which validity arguments on its generalization to various subpopulations could be strengthened and score interpretability could be improved.