Maugeri respiratory failure questionnaire reduced form : a method for improving the questionnaire using the Rasch model

Purpose. The Maugeri Respiratory Failure questionnaire (MRF-28) is the first instrument specifically developed for use with chronic respiratory failure (CRF) patients. The 28 items were selected using classical test theory. The purpose of the current analysis was to further refine the questionnaire using item response theory, specifically, the Rasch model analysis. Methods. Three hundred and seventeen CRF patients (mean aged 66.7 yrs; Male 219, Female 98) completed the MRF-28 health status measure. Data were collected through the self-report questionnaire and analyzed using 1-parameter logistic models by means of RUMM software. Results. The 28-item questionnaire has good psychometric properties in terms of discriminant power because the Person Separation Index is 0.896. However, the item-trait interaction was not good as shown by the total-item Chi-square (χ1122 = 182.7, p < 0.001). Removing two items that did not fit the Rasch model well, produced a minor improvement in Person Separation Index to 0.899 and the item-trait interaction improved (χ1042 = 127.1, p = NS). In the preliminary analysis we identified 21 patients who were outliers; when they were excluded the distribution of the residuals, according to the Kolmogorov-Smirnov statistics, was normal and factor analysis of the item residuals showed that the components had similar eigenvalues and no strong correlation with items. These results suggest that the MRF-26 is a unidimensional measure of health-related quality of life impairment for chronic respiratory failure patients. Conclusions. A combination of classical psychometric tests and Rasch analysis produced an instrument of moderate size that covers a wide range of effects of CRF and has interval scaling properties.