1999 Clinical and Scientific Meeting

P. De Becker, I. Campine, E. Joos, K. de Meirleir.

Human Physiology and Medicine
Vrije Universiteit Brussel, Brussels, Belgium

Predicting Physical Disability in Patients with Chronic Fatigue Syndrome


Individuals with chronic fatigue syndrome (CFS) commonly experience limitations in their ability to perform physical activities. They are often so limited by their illness that they note an inability to perform even routine daily activities, and they are also unable to carry out job-related functions in the workplace.

In order to develop a framework for determining physical impariment we will describe the results of our research on exercise capacity, use the American Medical Association guidelines for impairment rating of the respiratory system and use our results to develop an impairment rating system for CFS.


513 CFS patients (427 female and 86 male) who fulfilled the 1988 CDC criteria for CFS and 372 healthy controls (204 female and 168 male) performed a maximal exercise test on an electrically braked bicycle ergometer and continuous gas exchange measurements were made. The groups were matched for sex and age.


The maximum oxygen consumption was respectively 19.86 ± 5.5 ml/min/kg (female CFS patients) and 32.04 ± 8.3 ml/min/kg (female controls); 24.93 ± 6.3 ml/min/kg (male CFS patients) and 36.4 ± 9.4 ml/min/kg (male controls). According to the AMA Guidelines for Impairment Rating (Table 1), female CFS patients have a degree of impairment of 30-45% which means a moderate impairment of the whole person; male CFS patients had a Class 2 impairment (mild impairment of the whole person). As expected the controls had no impairment.

Table 1

Class 1

Class 2

Class 3

Class 4

Degree of Impairment


10 - 25%

30 - 45%

50 - 100%


No impairment of the whole person

Mild impairment of the whole person

Moderate impairment of the whole person

Severe impairment of the whole person

Maximal oxygen consumption

> 25ml/min/kg

20 - 25ml/min/kg

15 - 20ml/min/kg

< 15ml/min/kg


Both female and male patients are limited in their capacity to perform physical activities. We suggest that exercise testing with measurement of maximum oxygen uptake can be used to determine the degree of physical disability in these patients. In a second stage we will more extensively analyse these results and calculate what percentage of our CFS population is severely, moderately or mildly impaired.


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