A Comparison of the 1988 and 1994 Diagnostic Criteria for Chronic Fatigue Syndrome
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Journal of Clinical Psychology in Medical Settings Vol. 8, No. 4, pp 337-343
Date: December 2001
Leonard A. Jason,(1,2) Susan R. Torres-Harding,(1) Renee R. Taylor,(1) and Adam
W. Carrico(1)
Chronic Fatigue Syndrome (CFS) is an illness that involves severe, prolonged
fatigue as well as neurological, immunological, and endocrinological system
pathology (Friedberg & Jason, 1998). Despite years of research, CFS remains
a poorly understood and controversial disease (Jason, et al., 1995). CFS has
been difficult to define because the exact causal agents are unknown, physical
signs and symptoms are variant, and diagnostic laboratory tests have poor
sensitivity and specificity (Bates et al., 1992; Holmes, 1991).
In 1988, Holmes, Kaplan, Gantz, et al. (1988) constructed the first U.S. working case definition of CFS. However, as the 1988 criteria were utilized in
research and practice, it became evident that there were numerous
inconsistencies in interpretation and classification (Holmes, Kaplan, Gantz, et
al., 1988; Matthews, Lane, & Manu, 1988; Schluederberg, et al., 1992;
Straus, 1992). Katon, Buchwald, Simon, Russo, and Mease (1991) found that
patients with CFS were indistinguishable from those with symptoms of chronic
fatigue not meeting the 1988 CDC criteria. A major area of concern with the
original CFS criteria was that the requirement of eight or more minor symptoms
could inadvertently select for individuals with psychiatric problems (Straus,
1992). Katon and Russo (1992) noted that chronic fatigue patients with the
highest number of unexplained physical symptoms had very high rates of
psychiatric disorders whereas patients with the lowest number of unexplained
symptoms displayed rates of psychiatric disorders that were similar to other
clinic populations with chronic medical illness.
These difficulties were influential in the development of a revised U.S. case definition for CFS by Fukuda et al. (1994). In this revised 1994 definition, a
patient is required to experience chronic fatigue of a new or definite onset
(for 6 or more months), that is not substantially alleviated by rest, not the
result of ongoing exertion, and produces significant reductions in occupational,
social, or personal activities. The 1994 criteria also require the concurrent
occurrence of at least four of eight minor symptoms.
Several investigations have contrasted the two U.S. case definitions of
CFS. In a study of 2,376 primary care patients, 1.2% of the sample were
diagnosed with CFS by using the 1988 case definition, compared to 2.6% using
the 1994 case definition (Wessely, Chalder, Hirsch, Wallace, & Wright,
1997). Tiersky et al. (2000) investigated the differences between the 1988 and
1994 case definition criteria in a study of 71 primary care patients with
CFS. Participants meeting only the 1994 definition experienced a greater
duration of illness than those meeting the 1988 definition. In contrast, those
in the 1988 group reported greater frequency of sore throats, joint pain,
tender lymph nodes, headaches, and fever. Finally, the 1988 group was more
likely to report a sudden illness onset and a greater reduction in premorbid
activity levels than the 1994 group.
In the present study, patients diagnosed with CFS according to the more
stringent 1988 criteria were compared to those who met only the 1994 criteria
and to those with fatigue due to psychiatric causes on measures of psychiatric
comorbidity, symptom frequency, and functional impairment. It was hypothesized
that the 1988 criteria, in comparison to the 1994 criteria, would identify a
patient group with more psychiatric comorbidity, symptoms, and functional
impairment.
METHOD
Procedure
The data was derived from a larger community-based study of CFS carried out in
three stages (Jason, Richman, et al., 1999). Stage 1 entailed a cross-sectional
screening telephone survey of a random sample of 28,673 households, with 18,675
adults completing the screening interview (65.1% completion rate). Stage 2
involved a structured psychiatric interview for those respondents from Stage 1
who screened positive for CFS (i. e., 6 or more months of fatigue, and at least
four minor symptoms based on the Fukuda et al., 1994, CFS criteria). In Stage 3, a physician conducted a detailed medical examination to rule out exclusionary medical conditions. A
team of four physicians and a psychiatrist were responsible for making a final
diagnosis, with two physicians independently rating each file, using the current
U. S. case definition of CFS. Where physicians disagreed, a third physician
rater was used (see Jason, Richman et al., 1999). For the purpose of the
present study, we focus on those 32 individuals who were diagnosed with CFS by
using the 1994 Fukuda case definition, and 33 with chronic fatigue explained by
psychiatric reasons (CF-Psychiatric). (3)
Definitions
1988 Criteria
To be classified with fatigue according to the 1988 criteria (Holmes, Kaplan,
Gantz, et al., 1988), participants needed to report 6 or more months of
persistent or relapsing, debilitating fatigue that does not resolve with bed
rest. Also, participants were required to report at least 8 of 11 minor
symptoms (fever or chills, sore throat, lymph node pain, muscle weakness,
muscle pain, postexertional malaise, headaches of a new or different type,
migratory arthralgias, neuropsychiatric complaints, sleep disturbance, and a
sudden onset of symptoms). Participants were also required to report at
least a 50% impairment of daily functioning, as compared to premorbid
levels. Exclusionary criteria, as defined by Holmes, Kaplan, Gantz, et
al. (1988) and Holmes, Kaplan, Schonberger, et al. (1988), were used. Fourteen
of the 32 individuals diagnosed with CFS by using the Fukuda's 1994 criteria, also
met the more stringent 1988 criteria.
1994 Criteria
Physicians utilized the current U. S. case definition in their diagnoses of CFS
after a thorough medical examination (Fukuda et al., 1994). To be diagnosed
with CFS, participants were required to experience persistent or relapsing
fatigue for a period of 6 or more months as well as the concurrent occurrence
of four or more minor symptoms that did not predate the illness and persisted
for 6 or more months since onset. Minor symptoms of the current U.S. case
definition of CFS included sore throat, lymph node pain, muscle pain, joint
pain, postexertional malaise, headaches of a new or different type, memory and
concentration difficulties, and unrefreshing sleep. Furthermore, the
participant had to experience substantial reductions in occupational,
educational, social, or personal activities as a result of their illness. Exclusionary
illnesses as defined by Fukuda et al. (1994) were used. As mentioned
earlier, 32 individuals were diagnosed with these criteria.
A Comparison of Diagnostic Criteria
Measures
Symptom Occurrence
Participants were also asked to complete the CFS Symptom Rating Form. Using
this form, participants indicated whether the eight CFS definitional symptoms
(Fukuda et al., 1994) occurred over the last 6 months constantly or repeating
regularly. Jason, Ropacki, et al. (1997) used a modified version of this form,
which was demonstrated to have high test-retest reliability over a 2-week
period (test-retest agreement: 76-92%).
Medical Outcomes Study
Participants completed the Medical Outcomes Study 36-item Short-Form Survey
(MOS) (Ware & Sherbourne, 1992; Ware, Snow, Kosinski, & Gandek, 2000),
a reliable and valid measure that discriminates between gradations of
disability. This instrument encompasses multi-item scales that assess physical
functioning, role limitations, social functioning, bodily pain, general mental
health, vitality, and general health perceptions. Higher scores indicated
better health, lower disability, or less impact of health on functioning. Reliability
and validity studies for the 36-item version of the MOS have shown adequate
internal consistency, discriminant validity among subscales, and substantial
differences between patient and non-patient populations in the pattern of
scores (McHorney, Ware, Lu, & Sherbourne, 1994; McHorney, Ware, &
Raczek, 1993; McHorney, Ware, Rogers, Razek, &Lu, 1992). The MOS Physical
Composite Score (PCS) and Mental Composite Score (MCS) were also utilized in
the present investigation as combined measures of the eight MOS subscales to
rate overall impairment of functioning (Ware, Kosinski, & Keller,
1994). These PCS and MCS have appropriate validity and reliability as
well as greater sensitivity and specificity in discriminating the gradations of
health status among groups (Brazier et al., 1992).
Degree of Impairment
Participants were asked to rate the degree to which their fatigue has impaired
their functioning in daily activities on a 100-point scale, with 0= no
difficulties and 100= total and complete disability.
Psychiatric Diagnoses
The Structured Clinical Interview for the DSM-IV (SCID) (Spitzer, Williams,
Gibbon, & First, 1995) was administered to provide current and lifetime
psychiatric diagnoses as defined on Axis I of the Diagnostic and Statistical
Manual of Mental Disorders - Fourth Edition (DSM-IV) (American Psychiatric
Association, 1994). The SCID is a valid and reliable measure semi-structured
interview that approximates a psychiatric interview (Rubinson & Asnis,
1989). Trained advanced clinical psychology graduate students with
master's degrees administered the SCID. The SCID provides for specification of
current and past psychiatric disorders. Using this specification of current and
past disorders, two indices were developed to indicate if a person met criteria
for at least one current psychiatric disorder, and if a participant met
criteria for at least one lifetime (i. e., past or current) psychiatric
disorder.
RESULTS
Thirty-two participants were diagnosed with CFS, using Fukuda et al. (1994)
case definition; 14 also met the more stringent 1988 criteria (Holmes, Kaplan,
Gantz, et al., 1988). Comparisons were made between the 14 participants who met
the 1988 criteria (1988 group), the 18 participants who met only the 1994
criteria (1994 only group), and the 33 participants whose fatigue was explained
by a psychiatric illness (CF psychiatric group).
Using chi-square analyses, participants in the 1988, 1994, and CF Psychiatric
groups did not significantly differ on socio-demographic variables or the
sudden onset of symptoms (See Table I). However, the 1988, 1994, and CF
Psychiatric groups differed significantly in rates of current,
chi^2(1,64)=8.64, p<.05, and lifetime chi^2(1,64)=7.41, p<.05,
psychiatric diagnoses. The 1988 and 1994 groups only had significantly
fewer current and lifetime psychiatric diagnoses than the CF Psychiatric group.
Chi-square analyses were performed to examine the overall differences among the
1988, 1994, and CF Psychiatric groups for the occurrence of the eight minor
symptoms in the current U. S. case definition of CFS (see Table II). Results
indicated that the groups differed significantly overall in the frequency of
sore throat pain, chi^2(2, 65)=6.27, p<.05, and lymph node pain chi^2(2,
65)=15.54, p<.01. The 1988 group reported significantly higher rates of sore
throat pain and lymph node pain than the 1994 group. Furthermore, those
participants meeting the 1988 criteria had significantly higher rates of sore
throat pain and lymph node pain than the CF Psychiatric group.
One-way ANOVAs were conducted examining MOS scores and participant ratings of
impairment of functioning in daily activities. These analyses were
significant overall for the general health subscale of the MOS, F(2,57)=3.18,
p<.05; the bodily pain subscale of the MOS, F(2,60)=3.16, p=.05; the PCS,
F(2,50)=3.81, p<.05; and participant self ratings of impairment of
functioning in daily activities, F(2,59)=4.82, p<.05. Bonferroni post hoc
analyses indicated that participants in the 1988 group had poorer general
health functioning than those in the 1994 group only. The 1988 group also had
significantly more bodily pain and lower PCS scores than the CF Psychiatric
group. Finally, in the self-reports of the degree of impairment of functioning
in daily activities, the 1994 group only reported significantly less impairment
than the CF Psychiatric group.
DISCUSSION
This study examined differences in socio-demographic characteristics, symptom
frequency, and functional impairment with individuals meeting different
diagnostic criteria sets for CFS. When samples of individuals meeting each of
the two U. S. definitional criteria for CFS were compared (1988 vs. 1994),
findings revealed no socio-demographic or psychiatric differences between the
two samples. However, important differences did emerge between the
two CFS diagnostic groups with respect to symptom frequency and functional
impairment. Our findings indicate that the 1988 group is more impaired in
measures of symptom frequency as well as functional impairment. This suggests
that the 1988 criteria appears to select a more symptomatic and impaired group
of individuals than the 1994 and psychiatrically fatigued groups.
Results are consistent with Tiersky et al. (2000), who also found increased
occurrence of sore throat pain and lymph node pain in the 1988 group when
compared to the 1994 group. However, Tiersky et al. (2000) also reported that
the 1988 group was more significantly likely to experience joint paint and
headaches when compared to the 1994 group only. Upon closer examination, the
frequency of the 1994 definitional symptoms reported in the Tiersky study is
generally higher in the 1988 group than the reported occurrence of these
symptoms in the present investigation's 1988 group. Additional findings
reported by Tiersky et al. (2000) may be due to their clinic-based sample such
that participants could have experienced a more severe illness with a greater
number of symptoms.
In relation to the two U.S. CFS criteria groups, the CF-explained psychiatric
group evidenced less symptom frequency, and less functional impairment than the
1988 group, but perceived themselves more functionally impaired than the 1994
group. Predictably, the CF-explained psychiatric group also evidenced the
highest frequency of current and lifetime psychiatric disorders.
A central strength of this study is that it is the first of its kind to use
random epidemiological methods to empirically compare the 1988 and the 1994
diagnostic criteria for CFS. It also re-examines the role of psychiatric
disorders in relation to different diagnostic criteria sets. Findings
should be interpreted within the context of limitations on statistical power
imposed by a small sample size. Because some differences between groups may
have not been detected, more research with larger samples is necessary to
replicate these results.
Studies examining sources of diagnostic unreliability have shown that subject,
occasion, and information variance account for only a small portion of
diagnostic reliability (Spitzer, Endicott, & Robins, 1975). However,
criterion variance, differences in the formal inclusion and exclusion criteria
used by clinicians to classify patients' data into diagnostic categories,
accounts for the largest source of diagnostic unreliability. The two U.S. definitions of CFS would be improved if more attention was devoted to developing
operationally explicit, objective criteria and standardized interviews (Jason,
King, et al., 1999).
In summary, participants meeting the 1988 criteria appear to be a more
symptomatic and functionally impaired group than those meeting the 1994
criteria only. Furthermore, these differences do not appear to be influenced by
psychiatric variables, as they occurred in the absence of differences in rates
of psychiatric comorbidity between the two groups. Taken together, these
findings indicate that the 1988 criteria may identify a distinct group of
individuals who not only have a higher frequency of CFS symptoms, but also
experience greater functional disability. Possibly because of the lesser degree
of specificity in criteria, individuals in the 1994 group may comprise more
heterogeneous patient groups experiencing more variability and wider ranges of
illness severity and functional disability.
ACKNOWLEDGMENT
Financial support for this study was provided by NIAID Grant No. AI36295.
TABLES
|
Table I |
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|
|
1994 but not |
|
|
|
Gender |
|
|
|
|
|
Age |
|
|
|
|
|
Ethnicity |
|
|
|
|
|
Marital Status |
|
|
|
|
|
Children |
78.6 |
50.0 |
48.5 |
|
|
At least one current psychiatric diagnosis |
53.8 |
55.6 |
87.9 |
* |
|
Lifetime psychiatric |
76.9 |
83.3 |
100 |
* |
|
Work status |
|
|
|
|
|
SES |
|
|
|
|
|
Sudden illness onset |
23.1 |
5.6 |
15.6 |
|
|
Note. Similar letters next to two columns indicate they are
significantly different at the p<.05 level using chi-square
analyses. Values represent percentages. |
||||
|
Table II |
||||
|
|
|
1994 but not |
CF psychiatric |
|
|
|
|
|
|
|
|
MOS(b) |
|
|
|
|
|
Physical health composite |
30.9 (a) |
37.0 |
39.9 (a) |
* |
|
Mental health composite |
39.1 |
38.9 |
33.1 |
|
|
Degree of impairment (b) |
64.1 |
46.5 (b) |
65.6 (b) |
* |
|
Note. Similar letters next to two columns indicate that they are
significantly different at the p<.05 level using Bonferroni post hoc
analyses. |
||||
FOOTNOTES
|
1. |
DePaul University, Chicago, Illinois. |
|
2. |
Correspondence should be addressed to Leonard A. Jason, Department of Psychology, 2219 N. Kenmore, Chicago, Illinois 60614. |
|
3. |
While 56 participants were diagnosed as having a psychiatric reason for their fatigue, the present study excluded the 23 individuals in this group with fatigue explained by substance abuse. |
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