RETURN TO TABLE OF
Selecting a Fatigue Rating Scale
By Fred Friedberg, PhD and
Leonard A. Jason, PhD
Measuring changes in patient fatigue levels is essential to the proper
treatment and research of chronic fatigue syndrome (CFS). However, the term
“fatigue” continues to elude precise definition or objective measurement in the
research literature. Because of this, the patient’s reported perception of his
or her fatigue has become the focus of fatigue measures.
There remains no “gold standard” of fatigue severity available to validate
fatigue scales, nor can these measures distinguish fatigue related to physical
exertion, emotional stress, pain, sleep disturbance, depression or the poorly
understood causal mechanisms of CFS. Fortunately, recently developed measures of
subjectively experienced fatigue, modeled after the measurement of other
subjective states (e.g., pain, anxiety), have multiple applications in clinical
and research settings. Based on a previous review of fatigue
instruments1 as well as more recent data, this article describes
selected fatigue measures for two categories of fatigue scales (fatigue
intensity and fatigue/function), and concludes with recommendations about the
use of fatigue scales by clinicians and researchers.
Measures of fatigue have one of the following response formats: verbal
ratings, visual analogue or numerical ratings. (Because the visual analogue
scale is rarely used and presents some difficulties, we will not discuss it.) A
verbal rating scale is a list of adjectives that describes different levels of
fatigue intensity, such as mild and moderate. The verbal rating scale is easy to
administer and score, easy for the respondent to comprehend, and compliance is
Alternatively, the numerical rating scale instructs the patient to provide a
single rating of his/her fatigue-related problem on a 0-to-10 or a 0-to-100
scale. The 0 point indicates no fatigue-related problem and the 10 or 100 point
indicates a fatigue-related problem as bad as it could be. The number chosen by
the patient signifies the severity of the fatigue-related problem for the
patient. Numerical rating scales of fatigue are extremely easy to administer and
score and have shown sensitivity to treatment effects in CFS.
Fatigue Intensity Scales
Selecting a fatigue intensity scale
may become a matter of the practical issues of patient comprehension and ease of
administration and scoring.
The Fatigue Scale is a 14-item verbal rating measure of fatigue
intensity2 with a four-choice response format that was developed with
a sample of 374 general medical outpatients. The scale showed strong internal
consistency and factor analysis yielded two dimensions, physical and mental
fatigue. Physical fatigue refers to items such as “I get tired easily,” “I can
no longer start anything” and “I feel weak,” while mental fatigue encompassed
difficulties with concentration and memory. The Fatigue Scale has also shown
sensitivity to treatment changes.
The limitations of the Fatigue Scale include its inability to distinguish
between CFS and primary depression patients, an important diagnostic issue in
CFS. In addition, a second factor analytic study of the Fatigue Scale in CFS
patients3 calls into question the stability of the factor structure
of the scale.
The Energy/Fatigue Scale is another verbal rating scale of
fatigue intensity.4 It consists of five questions with a five-choice
response format containing adjectives describing both fatigue (worn out, tired)
and energy (pep, energy). It was derived from the Rand Vitality Index and was
given to 2,389 adults visiting ambulatory medical clinics. The measure showed
good internal consistency.4 The brevity of the Energy/Fatigue Scale
may result in scores that do not fully reflect the severity of illnesses such as
CFS. No published study has specifically tested the psychometric properties of
the Energy/Fatigue Scale in CFS.
Fatigue/function scales quantify
the linkage between fatigue intensity and functional limitations. Clearly, two
patients with similar levels of fatigue severity in CFS may show widely
divergent levels of incapacity. Conversely, two patients with similar functional
limitations may show substantially different levels of fatigue severity.
The Fatigue Severity Scale is composed of nine items with a
seven-point response format.5 Sample questions include “I am easily
fatigued” and “Exercise brings on my fatigue.” In the initial validation study,
internal consistency for the Fatigue Severity Scale was high for specific
illness groups (MS and lupus) and healthy controls. The scale clearly
distinguished patients from controls and it was moderately correlated with a
single-item visual analogue scale of fatigue intensity. In all patients,
clinical improvement in fatigue was associated with reductions in scores on the
Fatigue Severity Scale.
In a recent study6 that compared the Fatigue Severity Scale to the
Fatigue Scale, both were found to be useful measures of fatigue-related
symptomatology within a general population of individuals with varying levels of
fatigue. However, the Fatigue Severity Scale appeared to represent a more
accurate and comprehensive measure of fatigue severity and functional disability
for individuals with CFS-like symptomatology.
The Fatigue Severity Scale is also a practical measure due to its brevity and
ease of administration and scoring. On the other hand, a ceiling effect in the
Fatigue Severity Scale may limit its utility to assess severe fatigue-related
disability. There-fore, the true association between the Fatigue Severity Scale
and other health-related measures may be underestimated.
The Checklist Individual Strength (CIS) is a 20-item
self-report questionnaire7,8 that captures four dimensions of
fatigue, including subjective experience of fatigue, reduction in motivation,
reduction in activity and reduction in concentration. Respondents rate the
extent to which each statement is true for them in the past two weeks on a
seven-point Likert scale ranging from 1 = “Yes, that is true” to 7 = “No, that
is not true.”
The CIS has demonstrated satisfactory psychometric properties, including high
internal consistency and the ability to discriminate healthy individuals,
patients with CFS and patients with multiple sclerosis.9 Finally, the
CIS has shown sensitivity to treatment intervention in a randomized clinical
trial of cognitive behavioral intervention for patients with CFS.10
However, the dimensions of the CIS, which may well characterize clinical
depression as well as CFS, have not been tested within a primary depression
population. Thus it is unknown if the CIS can differentiate the two
Is Fatigue Qualitatively Different in CFS?
The above fatigue scales
have confirmed that subjectively rated fatigue severity is often higher in CFS
than in other fatiguing illnesses. However, severity measures do not address
qualitative aspects of the fatigue experience. CFS patients often describe
unusual fatigue sensations that, according to a descriptive study of 313 CFS
patients,11 may be useful in diagnosing the illness.
The 19-item, self-report Fatigue Qualities Scale
descriptions of fatigue symptoms commonly found in a variety of medical
conditions that may be associated with CFS, including subclinical
hypothyroidism, glycogen storage disease and mitochondrial dysfunction. Sample
items include: “My arms feel ‘heavy’ and ‘dead’ when I’m not moving them,”
“Climbing stairs feels like swimming against a strong current of molasses” and
“I have to consciously think about a movement and concentrate before I can
A discriminant analysis using Fatigue Qualities Scale
scores correctly classified 91–97 percent of self-identified CFS patients and
healthy significant others. In comparison, a self-report inventory of CFS
symptoms based on theU.S. case
definition12 correctly classified only 67 percent of these patients
and 85 percent of healthy significant others. A replication of these findings
would be necessary to confirm the potential utility of the Fatigue Qualities
Scale in diagnostic evaluations of CFS.
Psychometric considerations would suggest the use
of fatigue scales that (1) have been diagnostically validated in CFS and
depression samples, (2) assess several factorially distinct dimensions of
fatigue and (3) are easy to administer and score. Unfortunately, none of the
above measures meet all of these criteria. Based on our own clinical and
research experience with fatigue measures, we would recommend for the clinician
the Fatigue Severity Scale, which provides a rapid assessment of fatigue-related
impairments (see table). For the researcher, the selection of any two fatigue
instruments may offer a more thorough description of the fatigue experience and
an opportunity for concurrent validation of each scale as well as convergent
validation with other measures.
Fred Friedberg is clinical assistant professor of psychiatry at the
York at Stony
Leonard A. Jason is director of the Center for Community Research at
The Fatigue Severity
The Fatigue Severity Scale can be used to monitor change in fatigue over time
or in response to therapeutic interventions. Patients are asked to respond to
each statement on a scale of 1 to 7, with 1 indicating “Strongly Disagree” and 7
indicating “Strongly Agree.”
My motivation is lower when I am
Exercise brings on my fatigue.
I am easily fatigued.
Fatigue interferes with my physical
Fatigue causes frequent problems for
My fatigue prevents sustained
Fatigue interferes with carrying out
certain duties and responsibilities.
Fatigue is among my three most
Fatigue interferes with my work, family or social life.
Score = Sum of responses divided by 9. Higher score indicates higher fatigue
This scale is reprinted with permission.5
Friedberg F and Jason
Understanding chronic fatigue syndrome: An
empirical guide to assessment and treatment. 1998;
: American Psychological
Chalder T et al. Development of a fatigue scale. J Psychosom Res.
Morriss RK et al. Exploring the validity of the Chalder fatigue scale in
chronic fatigue syndrome. J Psychosom Res. 1998; 45:
Ware JE et al. The MOS 36-item Short-Form Health Survey (SF-36) I:
Conceptual framework and item selection. Medical Care. 1992; 30:
Krupp LB et al. The Fatigue Severity Scale: Application to patents with
multiple sclerosis and systemic Lupus erythematosus. Arch Neurol. 1989;
Taylor R et al. Fatigue rating scales: an empirical comparison.
Psychol Med, 2000; 30: 849-856.
Vercoulen JHMM et al. Dimen-sional assessment of chronic fatigue
syndrome. J Psychosomc Res. 1994; 38; 383-392.
Beursken AJHM et al. Fatigue among working people: Validity of a
questionnaire measure. Occ Envir Med. 2000; 57:353-7.
Vercoulen JHMM et al. The measurement of fatigue in patients with
multiple sclerosis: a multidimensional comparison with chronic fatigue
syndrome and healthy subjects. Arch Neurol. 1996; 53:642-9.
Prins JB et al. Cognitive behaviour therapy for chronic fatigue syndrome:
a multicentre randomised controlled trial. Lancet. 2001; 357:
Dechene L et al. A qualitative fatigue scale for chronic fatigue
syndrome. Paper presented at the meeting of the American Association for
Chronic Fatigue Syndrome, Ft. Lauderdale,
Fukuda K et al. The chronic fatigue syndrome: A comprehensive approach to
its definition and study. Annals of Internal Medicine. 1994;