A screening instrument for chronic fatigue syndrome: Reliability and validity

Because estimates of the prevalence of Chronic Fatigue Syndrome (CFS) have been quite variable, there is a need for a screening instrument and second stage medical assessment that will produce the most valid estimate of the CFS prevalence. In the present study, four groups of 15 subjects each were recruited: patients diagnosed with (1) CFS, (2) Lupus, (3) Multiple Sclerosis (MS), and (4) a healthy control group. Participants were interviewed twice over a two week period of time with a screening instrument comprising The Fatigue Scale and a newly configured section. The screening instrument had excellent test-retest and interrarer reliability. This screening instrument therefore has utility for CFS community-based epidemiologic research. However, while the instrument differentiates patients with CFS from those who are healthy, it is less likely to distinguish CFS from other autoimmune diseases (especially Lupus). Thus, future community- based CFS prevalence studies should encompass both a screening and a medical examination to adequately differentiate CFS from other illnesses with overlapping symptomatology. We recommend a two-stage research design with (1) a screening instrument with good sensitivity and (2) medical assessments of CFS positives from stage 1 to deal with the specificity problem.