Cross-cultural validation of the Chalder Fatigue Questionnaire in Brazilian primary care.

OBJECTIVE The Chalder Fatigue Questionnaire (CFQ) is an instrument used to measure physical and mental fatigue. We translated and adapted the questionnaire and tested its reliability and validity in a Brazilian primary care setting. METHOD A pilot study with 204 consecutive primary care attenders in Sao Paulo, Brazil, verified the internal consistency and factor structure of the questionnaire. After some modifications through a rigorous translation, back-translation, and cross-cultural adaptation procedure, a validation study was conducted with 304 attenders, who also completed the fatigue section of the Revised Clinical Interview Schedule (CIS-R). RESULTS The internal consistency of the Brazilian CFQ slightly improved from the pilot to the validation study: Cronbach's alpha from .86 to .88. The two-factor structure (physical and mental fatigue) also improved. According to the receiver operating curve analysis with the fatigue section of the CIS-R as the standard criterion, 3/4 was chosen as the cutoff for Brazilian primary care (sensitivity 69.1% and specificity 79.4%). CONCLUSION The Brazilian CFQ had good reliability and validity. The cutoff was determined as 3/4 and the factor structure of the English CFQ was closely reproduced.