Construct and criterion validity of the DUFS and DEFS4 in Lithuanian patients with coronary artery disease

BACKGROUND: Fatigue has become an important symptom in clinical diagnosis and clinical trials among subjects with cardiovascular diseases and disease-specific fatigue scales were developed in a Dutch and English version. OBJECTIVE: Various questionnaires for measuring fatigue have been developed, but currently no validated questionnaire targeted at subjects with cardiovascular disease and heart failure exists in the Lithuanian language. METHODS: Despite the rigor of the exploratory factor analysis and analyses of the psychometric properties of the disease-specific Dutch Fatigue Scale and the Dutch Exertion Fatigue Scale (DUFS-DEFS) we adopted a confirmatory approach considered as the gold standard method for the evaluation of construct validity in psychometric inventories. To test the criterion validity of the DUFS and DEFS structural equation modelling was employed with the widely used and validated Multidimensional Fatigue Inventory (MFI). RESULTS: The a priori specification of a hypothesized five-factor model of the MFI-20 and a two-factor model of the DUFS and DEFS appeared to have a good fit to the data in Lithuanian patients. The hypothesized model of the criterion validity of the DUFS and DEFS had a good fit and classes of disease severity showed statistically significant and clinically relevant differences on fatigue scores. CONCLUSION: The construct validity and criterion validity of the DUFS and DEFS were confirmed in a Lithuanian sample of cardiac patients. The construct validity of the MFI was also supported and this fatigue measure can be used in Lithuanian settings of clinical practice and research.