Abstract
Background: A diagnostic instrument, the CFS Questionnaire, was developed for clinicians and researchers to administer to their patients as a screening instrument for CFS. The CFS Questionnaire is comprehensive, covering the inclusionary and exclusionary self-report criteria of the current U.S. case definition (4). The instrument also assesses past and current activity levels, and symptoms of post-exertional malaise to ensure these items are adequately assessed.
Objectives: The goal of the present study was to evaluate the diagnostic reliability of an experimental measure for assessing chronic fatigue syndrome (CFS).
Methods: This instrument was administered to 15 persons with CFS, 15 persons with major depressive disorder (MDD), and 15 controls. Using the Fukuda et al. (4) diagnostic criteria, raters independently reviewed participants' CFS Questionnaire responses and rated whether each study participant met criteria for chronic fatigue syndrome.
Results: This instrument demonstrated good inter-rater reliability. Further, this instrument demonstrated adequate classification accuracy, with a 9.3 positive likelihood ratio and a .08 negative likelihood ratio. Overall, the CFS Questionnaire demonstrated good test-retest reliability, with intra-class correlation coefficients and kappa coefficients at .70 or higher for most items. Lower test-retest reliability coefficients were found for some items assessing temporal symptoms or items requiring an estimate of time.
Conclusion: The present study suggests that the CFS Questionnaire is a reliable diagnostic tool. Use of the CFS Questionnaire should promote higher levels of diagnostic reliability because it allows for accurate classification of individuals with CFS.