Construct validity and reliability of the Sinhala version of the Chalder fatigue questionnaire in a cohort following dengue infection in Sri Lanka

The objective of the study was to culturally adapt, translate and assess the validity and reliability of the 11-item Chalder Fatigue Questionnaire (CFQ) among adults (18-60 years), confirmed with dengue infection, admitted to a tertiary hospital in Colombo District, Sri Lanka. Modified Delphi Technique was used in cultural adaptation and assessing, face, content and consensual validity. A descriptive cross-sectional validation study was conducted among 110 patients. CFQ was administered one month after having dengue fever in assessing post-infectious fatigue (PIF). CFQ-Sinhala version (CFQ-S) was assessed for construct validity and reliability. Construct validity of the CFQ-Sinhala version was described with hypothesized scale structure and with confirmatory factor analysis. The culturally adapted (CFQ-S) confirmed the original two-factor structure among adults after one month of having Dengue infection. CFQ-S demonstrated satisfactory internal consistency of ≥ 0.7. Cronbach’s alpha coefficient was 0.85 for the overall scale. The test-retest reliability was assessed by calculating the intra-class correlation coefficient between the two assessments and reported as 0.89 on the overall scale. The study confirmed satisfactory levels of validity and the reliability of the CFQ-S, as a valid tool to screen for PIF. The two-factor model described by the original author was confirmed as the best fitting model by triangulation of results.