Factor structure of the Quality of life in Reflux and Dyspepsia (QOLRAD) questionnaire evaluated in patients with heartburn predominant reflux disease

Abstract

Aim: To test whether the original factor structure of the Quality of Life in Reflux and Dyspepsia (QOLRAD) can be replicated in Nordic patients and English speaking patients. Patients and methods: Clinical trial patients with heartburn without esophagitis completed the Swedish, Norwegian, Finnish and Danish versions (n = 634) and the English version (n = 1185). The factor structure was examined using models generated by exploratory and confirmatory factor analysis. Results: The exploratory factor analysis suggested that the original five-factor structure solution was the most optimal. The Nordic versions explained 67% and the English version 72% of the variance. The factor loading of 22 out of 25 items was >0.55. In the confirmatory factor analysis, because of the sample size, only the Swedish and Norwegian data were used. Confirmatory factor analysis indicated an acceptable goodness of fit of the five-factor solution to the data with a goodness of fit index of 0.85 in the Swedish, 0.77 in the Norwegian and 0.91 in the English speaking population. The internal consistency reliability ranged from 0.70 to 0.94 (in the Nordic translations) and from 0.85 to 0.92 (in the English version), supporting the homogeneity of the items within the factors and thus their construct validity. The QOLRAD distinguished severity and frequency of heartburn, thereby documenting its known-group validity to distinguish between groups of patients. Conclusions: The factor structure and dimensionality of the English version and the Swedish and Norwegian translations of the QOLRAD could be replicated by the exploratory and confirmed by the confirmatory factor analysis. The QOLRAD is a valid and reliable instrument for use in clinical trials.