Chronic fatigue syndrome prevalence is grossly overestimated using Oxford criteria compared to Centers for Disease Control (Fukuda) criteria in a U.S. population study

Abstract

ABSTRACT Background: Results from treatment studies using the low-threshold Oxford criteria for recruitment may have been overgeneralized to patients diagnosed by more stringent chronic fatigue syndrome (CFS) criteria. Purpose: To compare the selectivity of Oxford and Fukuda criteria in a U.S. population. Methods: Fukuda (Center for Disease Control (CDC)) criteria, as operationalized with the CFS Severity Questionnaire (CFSQ), were included in the nationwide rc2004 HealthStyles survey mailed to 6175 participants who were representative of the U.S. 2003 Census population. The 9 questionnaire items (CFS symptoms) were crafted into proxies for Oxford criteria (mild fatigue, minimal exclusions) and Fukuda criteria (fatigue plus ≥4 of 8 ancillary criteria at moderate or severe levels with exclusions). The comparative prevalence estimates of CFS were then determined. Severity scores for fatigue were plotted against the sum of severities for the eight ancillary criteria. The four quadrants of scatter diagrams assessed putative healthy controls, CFS, chronic idiopathic fatigue (CIF), and CFS-like with insufficient fatigue subjects. Results: The Oxford criteria designated CFS in 25.5% of 2004 males and 19.9% of 1954 females. Based on quadrant analysis, 85% of Oxford-defined cases were inappropriately classified as CFS. Fukuda criteria identified CFS in 2.3% of males and 1.8% of females. Discussion: CFS prevalence using Fukuda criteria and quadrant analysis was near the upper limits of previous epidemiology studies. The CFSQ may have utility for on-line and outpatient screening. The Oxford criteria were untenable because they inappropriately selected healthy subjects with mild fatigue and CIF and mislabeled them as CFS. Abbreviations: CDC: Center for Disease Control; CFS: criteria requiring moderate or severe for fatigue and ancillary criteria; CFS: chronic fatigue syndrome; CFS-Like: CFS-like with insufficient fatigue syndrome; CFSQ: CFS Symptom Severity Questionnaire; CIF: chronic idiopathic fatigue; Oxford: 1991 Oxford criteria; SEID: systemic exertion intolerance disease; Sum8: sum of Severity Scores for the eight ancillary criteria