Operationalizing Substantial Reduction in Functioning Among Young
Adults with Chronic Fatigue Syndrome
Kristen D. Gleason
Ben Z. Katz
Leonard A. Jason
International Society of Behavioral Medicine 2018
Purpose Chronic fatigue syndrome and myalgic encephalomyelitis are fatiguing illnesses that often result in long-term impair-
ment in daily functioning. In reviewing case definitions, Thrope et al. (Fatigue 4(3):175–188, 2016) noted that the vast majority
of case definitions used to describe these illnesses list a “substantial reduction” in activities as a required feature for diagnosis.
However, there is no consensus on how to best operationalize the criterion of substantial reduction.
Method The present study used a series of receiver operating curve (ROC) analyses to explore the use of the Medical Outcomes
Study Short-Form-36 Health Survey (SF-36), designed by Ware and Shelbourne for operationalizing the substantial reduction
criterion in a young adult population (18–29 years old). We compared the sensitivity and specificity of various cutoff scores for
the SF-36 subscales and assessed their usefulness in discriminating between a group of young adults with a known diagnosis of
chronic fatigue syndrome or myalgic encephalomyelitis (n = 98) versus those without that diagnosis (n =272).
Results The four top performing subscales and their associated cutoffs were determined: Physical Functioning ≤ 80, General
Health ≤ 47, Role Physical ≤ 25, and Social Functioning ≤ 50. Used in combination, these four cutoff scores were shown to
reliably discriminate between the patients and controls in our sample of young adults.
Conclusion The implications of these findings for employing the substantial reduction criterion in both clinical and research
settings are discussed.
Keywords Chronic fatigue syndrome
CFS case definitions
Chronic fatigue syndrome (CFS) and myalgic encephalomyeli-
tis (ME) are illnesses characterized by fatigue, unrefreshing
sleep, exacerbation of symptoms following exertion, and cog-
nitive impairment, the combination of which often results in
drastically reduced levels of daily functioning . CFS has
been estimated to affect about a million individuals in the
USA . Efforts to better understand the illness have been
complicated by competing case definitions, each of which iden-
tifies differing combinations of symptoms required for the di-
agnosis of ME, CFS, or both. The majority of case definitions
specify Bsubstantial reduction in activity^ as a key characteristic
of the ME or CFS illness, making it one of the few criteria that
remain consistent across case definitions. This standard requires
evidence that an individual’s level of functioning has reduced
significantly from pre-illness levels. However, most case defi-
nitions have not described a reliable system for characterizing
this criterion . For example, the case definition developed by
Fukuda et al.  requires a decrease from pre-illness levels of
occupational, educational, social, or personal activities.
However, the authors do not specify methods for measuring
such activity levels, or standards to define the extent of the
functional decrease that should be considered substantial
enough to warrant a diagnosis.
The Canadian Clinical Criteria (CCC) casedefinition
specifies different levels of substantial reduction, with a Bmild
reduction^ defined as an approximately 50% decrease from
* Leonard A. Jason
University of Southern Maine, 512 Science Building, 96 Falmouth
Street, Portland, ME 04103, USA
Center for Community Research, DePaul University, 990 W
Fullerton Avenue, Suite 3100, Chicago, IL 60614, USA
Ann and Robert H. Lurie Children’s Hospital of Chicago, 225 E
Chicago Avenue, Chicago, IL 60611, USA
International Journal of Behavioral Medicine