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

Background: Results from treatment studies using the low threshold Oxford criteria for recruitment may have been overgeneralized to patients diagnosed by more stringent 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 6,175 participants who were representative of the US 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 8 ancillary criteria. The 4 quadrants of scatter diagrams assessed putative healthy controls, CFS, chronic idiopathic fatigue, and CFS-like with insufficient fatigue subjects.

Results: The Oxford criteria designated CFS in 25.5% of 2,004 males and 19.9% of 1,954 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 were 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 chronic idiopathic fatigue and mislabeled them as CFS.

Keywords: Chronic Fatigue Syndrome; chronic idiopathic fatigue; fatigue; myalgic encephalomyelitis; selection criteria.

Figures

Figure 1.

Quadrant method for the HealthStyles survey population. Sum8 (range 0 to 32) was binned and then plotted versus Fatigue Severity for the (a) 1,945 females and (b) 2,004 males who remained after removing subjects with incomplete questionnaire responses. Bar graphs were rotated to provide 2 orthogonal perspectives that showed the progressive increases in Fatigue Severity and Sum8 along the diagonal splines. The open row and column on each axis indicate the boundaries for significant fatigue and Sum8 ≥ 14. These boundaries defined HC, CFS-Like, CIF and CFS quadrants. Frequency distributions projected the Sum8 scores for each level of Fatigue Severity in (c) females and (d) males. A larger proportion of females had Fatigue Severity of “none” compared to males and accounted for the relatively lower proportion of CFS in females than males in this survey population.

Figure 2.

Quadrant analysis of females (n = 1,495). (a) The Oxford criteria permitted mild fatigue (green bars) which skewed the putative CFS subjects into healthy control and CFS-Like quadrants. (b) The rigorous CDC criteria limited subject selection to the CFS quadrant with moderate or severe fatigue and the sum of the 8 ancillary criteria scores (Sum8) from 14 to 32.

Figure 3.

Quadrant analysis of males (n = 2,004). (a) The Oxford criteria permitted mild fatigue (green bars) which skewed the putative CFS subjects into healthy control and CFS-Like quadrants. (b) The rigorous CDC criteria limited subject selection to the CFS quadrant with moderate or severe fatigue and the sum of the 8 ancillary criteria scores (Sum8) from 14 to 32.