Measuring the quality of life in hypertension according to Item Response Theory

Abstract

OBJECTIVE: To analyze the Miniquestionário de Qualidade de Vida em Hipertensão Arterial(MINICHAL – Mini-questionnaire of Quality of Life in Hypertension) using the Item Response Theory.METHODS: This is an analytical study conducted with 712 persons with hypertension treatedin thirteen primary health care units of Fortaleza, State of Ceará, Brazil, in 2015. The steps of theanalysis by the Item Response Theory were: evaluation of dimensionality, estimation of parametersof items, and construction of scale. The study of dimensionality was carried out on the polychoriccorrelation matrix and confirmatory factor analysis. To estimate the item parameters, we usedthe Gradual Response Model of Samejima. The analyses were conducted using the free softwareR with the aid of psych and mirt.RESULTS: The analysis has allowed the visualization of item parameters and their individualcontributions in the measurement of the latent trait, generating more information and allowingthe construction of a scale with an interpretative model that demonstrates the evolution of theworsening of the quality of life in five levels. Regarding the item parameters, the items relatedto the somatic state have had a good performance, as they have presented better power todiscriminate individuals with worse quality of life. The items related to mental state have beenthose which contributed with less psychometric data in the MINICHAL.CONCLUSIONS: We c onclude t hat t he i nstrument i s suitable f or t he i dentification of t heworsening of the quality of life in hypertension. The analysis of the MINICHAL using the ItemResponse Theory has allowed us to identify new sides of this instrument that have not yet beenaddressed in previous studies