Functional Capacity Index in Elderly: Construction through the Item Response Theory

Abstract

Background: The aim of the present study was to apply item response the-ory to measure the functional capacity index as an important measure of the component of positive aspects of functionality among elderly people, contri-buting to the expansion of the use of this tool by creating shorter and more precise scales for analysis of health situations. Methods: Cross-sectional study was performed, and sample consisted of 41,269 elderlies aged 60 or more from the 27 federal units that participated in the National Household Sample Survey, in 2008, in Brazil. The generalized partial credit model was used for the calibration of items. Results: The results of the analysis showed that the functional capacity index was sufficiently unidimensional for item response theory and, for greater reliability, the inclusion of more difficult items for elderly Brazilians with better functional capacity would be re-quired. Conclusions: Finally, the present study argues that the functional capacity index can be used as a tool in the analysis and prioritization of health situations.