chronic fatigue syndrome: assessing symptoms and activity level

Chronic Fatigue Syndrome: Assessing Symptomsand Activity Level

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Leonard A. Jason, Caroline P. King, Erin L. Frankenberry,and Karen M. JordanDePaul University

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Warren W. TryonFordham University

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Fred Rademaker and Cheng-Fang HuangNorthwestern University

Current approaches to the diagnosis and assessment of Chronic FatigueSyndrome (CFS) rely primarily on scales that measure only the occurrenceof various symptoms related to CFS. Such approaches do not provideinformation on either the severity of symptoms or on fluctuations in symp-tom severity and activity level that occur over time. As a result, thesemeasures do not reflect the complexities and the interrelations amongsymptoms. By obscuring the fluctuating nature of CFS and its high vari-ability, current assessment procedures may prevent health care profession-als from understanding the complexities of this disease. The present studyprovides two CFS case studies to illustrate the advantages of using self-reporting rating scales in combination with a device used to measure thefrequency and intensity of activity. The implications of this assessmentsystem, which captures the symptom dynamics and variability involved inCFS, are discussed. © 1999 John Wiley & Sons, Inc. J Clin Psychol 55:411–424, 1999.

The authors would like to thank Rhonda Frisbee for her help in data collection. Financial support for this studywas provided by NIAID grant number AI36295.Correspondence concerning this article should be addressed to Leonard A. Jason, Ph.D., Department of Psy-chology, DePaul University, 2219 N. Kenmore, Chicago, IL 60613.

JOURNAL OF CLINICAL PSYCHOLOGY, Vol. 55(4), 411–424 (1999)© 1999 John Wiley & Sons, Inc. CCC 0021-9762/99/040411-14

Several studies suggest that approximately 400,000 Americans might have Chronic FatigueSyndrome (cFs; Jason, Taylor, et al., 1995). Despite several years of research, CFS remainsa puzzling and poorly understood disease (Jason, Taylor, et al., 1997). One factor that hascontributed to the slow progress in research concerning CFS is a lack of consensus amonghealth care professionals regarding the diagnostic criteria for CFS (Holmes, 1991; Taylor& Jason, 1996). Attempts to specify diagnostic criteria for this syndrome historicallyhave sparked debate and considerable controversy (Grufferman, 1991).

Several definitions of CFS have been proposed (Fukuda et al., 1994; Holmes et al.,1988; Lloyd, Hickie, Boughton, Spencer, & Wakefield, 1990; Schluederberg et al., 1992;Sharpe et al., 1991). Unfortunately, none have been derived empirically (Bates et al.,1994; Jason, Wagner, et al., 1995). In the past few years, a majority of researchers havebegun using the Fukuda et al. (1994) diagnostic criteria, which require that two majorcriteria be met: (a) the presence of persistent or relapsing chronic fatigue for at least 6 ormore consecutive months that is of a new or definite onset and is neither the result ofongoing exertion nor alleviated by rest, and the fatigue must result in substantial reduc-tions in previous levels of occupational, educational, social, or personal activities; and (b)The concurrent occurrence of four or more of eight minor symptoms (e.g., sore throat,muscle pain) that must be persistent or recurrent during 6 or more months of the illnessand do not predate the fatigue (Fukuda et al., 1994). The symptom criteria for the eightminor symptoms are scored using binary classification (i.e., occurrence versus nonoccur-rence), and play a pivotal role in the assessment and diagnosis of this syndrome. Yetdespite the importance of these symptoms in defining CFS, current approaches to chart-ing and assessing symptoms rely on data collected at only one time point, and only theoccurrence of symptoms is assessed (Jason, Holden, et al., 1995; Jason & Taylor, 1994;Wood, Magnello, & Sharpe, 1992).

In addition to obscuring the variability that persons with CFS experience in theirsymptomatology, current rating scales also provide limited information on the high inter-personal variability of this disease. For example, two individuals may both indicate thepresence of a particular symptom; however, for one person the severity of the symptommay be mild whereas for the other it might be severe. In a study by Jason, Holden, Taylor,and Melrose (1995), two persons with CFS rated feverishness and fatigue on a 100-pointscale over the course of a day. Data revealed distinct patterns for the two participants. Forone participant, symptoms were rated as severe at all time points, even though activitylevel was low. For the other participant, increases and decreases in symptom severityfluctuated in relation to activity levels (Jason, Holden, et al., 1995). Scales that measurethe occurrence of symptoms but not their severity are not sensitive to these types ofdistinctions in symptomatology and interpersonal variability. Given that it is likely thatCFS is a heterogeneous disease with different subtypes of patients (Hickie et al., 1995;Holmes, 1991; Jason et al., 1995), instruments need to be sensitive to the interpersonalvariability in symptoms and fatigue levels to differentiate subsets of CFS patients.

Dechene, Friedberg, McKenzie, and Fontanetta (1996) have also noted the potentialfor CFS to be misdiagnosed when using the Fukuda et al. (1994) symptom criteria alone.In their study, Dechene et al. (1996) assessed CFS symptomatology in a healthy sampleof 179 adults known not to have CFS. Fifteen percent of this sample of healthy adults metthe Fukuda et al. (1994) symptom criteria for CFS. These findings strengthen the argu-ment that comprehensive and differentiated measures are needed to diagnose CFS withgreater accuracy.

Another perplexing problem for CFS researchers is the measurement of fatigue andactivity levels. The definition of CFS has not been informed by recent technologicaldevelopments in activity measurement and that activity reduction remains poorly defined

412 Journal of Clinical Psychology, April 1999

(Jason, Ropacki, et al., 1997). No guidelines have been provided for how to evaluate“substantial reductions” in activity level or energy level; thus, the development of mea-sures to assess fatigue and activity level has been problematic (Bell, 1991). To date,fatigue rating scales typically have been used to provide a sample describing one timepoint (Krupp, Mendelson, & Friedman, 1991). Because fatigue levels are such a promi-nent and defining symptom of CFS, a behavioral approach using time series methodsmight also provide some advantages in describing activity levels and fatigue in CFS.

Jason and Taylor (1994) developed an approach to the assessment of CFS symptomsto facilitate health care professionals’ understanding of this complex disease. They admin-istered a simple self-reporting rating scale on two occasions to a CFS patient on whichsymptoms were rated from 0 (no problem) to 10 (severe problem). Using this measure-ment system, Jason and Taylor were able to capture the changes in symptom severity,symptom dynamics, and symptom patterns that occur over time. Unfortunately, this studyoccurred before the new CFS case definition was published (Fukuda et al., 1994); there-fore, they did not assess all of the symptoms in the new case definition.

The present study was conducted to improve the Jason and Taylor (1994) measure-ment system by using a more differentiated and comprehensive version of the self-ratingscale in combination with an activity monitoring device. Among the most serious issuesraised is that self-report data may lead to erroneous research results more often thanpreviously thought. Self-report is unavoidable for some variables such as fatigue, whichis a complex psychological state that cannot yet be measured otherwise. This is clearlynot the case for activity for which objective, instrumented measurements are availableand constitute the gold standard. Tryon (1991) has reviewed instruments for measuringactivity level, and Tryon and Williams (1996) have described a new computerized acti-graph capable of measuring the intensity of activity and recording such values everyminute of the day and night for 22 consecutive days before filling memory. This technol-ogy for obtaining objective longitudinal activity measurements while the participant behavesin his or her natural environment can and should be used to further examine the constructof fatigue. In the present study, two CFS case studies and one control case study arepresented to illustrate the benefits and advantages of using these new assessment systems.

METHOD

Participants

Participants in the case studies were two middle-aged adults who had been diagnosedwith CFS by physicians using the Fukuda et al. (1994) case definition. In addition, acontrol participant also completed the symptom rating form. Both CFS participantsdescribed their prefatigue lifestyle as having been extremely active and stated that sincethe fatigue and related symptoms had begun, their activity levels confined them to theirhomes. Neither of the participants had medical illnesses that would exclude a CFS diag-nosis. The two CFS case studies illustrate the significant distinctions that occur amongpersons diagnosed with CFS. The cases were selected to represent the different coursesand clinical pictures of this illness. For each of the two participants with CFS, two phy-sicians had examined them and concluded that they met the symptom criteria for CFS,based on the Fukuda et al. (1994) criteria. In addition, they filled out several question-naires and, based on self-report data, the findings from the data clearly indicated that bothparticipants met the major and minor criteria for CFS. The control participant had beenexamined by a physician and there was no indication of CFS or any other chronic healthcondition that might cause fatigue.

Symptoms and Activity in CFS 413

Materials and Procedure

The Fatigue Scale.Participants were asked to complete the Fatigue Scale, an 11-itemself-rating scale developed by Chalder et al. (1993). The scale is designed to measure theseverity of mental, physical, and total fatigue by scoring responses to scale items. Exam-ples of items on the scale include questions such as “Do you have difficulty concentrat-ing” and “Do you have less strength in your muscles”. Participants are instructed torespond to each item on a 4-point rating scale, with higher numbers indicating moresevere problems (range 0–33).

The Fatigue Scale has been demonstrated to be a reliable and valid measure withhigh internal consistency (Chalder et al., 1993). In addition, a principal components analy-sis supported a two-factor solution: mental fatigue and physical fatigue. Cronbach’s alphafor the 11-item scale was .89. For the two sets of items, mental fatigue and physicalfatigue, Cronbach’s alpha was .85 and .82, respectively (Chalder et al., 1993). In a recentstudy by Jason et al. (1997), healthy control participants obtained an overall score on TheFatigue Scale of 4.53 (physical subscale5 3.27; mental subscale5 1.27), whereas thosewith CFS obtained an overall fatigue scale score of 27.53 (physical subscale5 18.40;mental subscale5 9.13).

CFS Symptom Rating Form.Participants were also asked to complete the CFS SymptomRating Form, on which they rated levels of fatigue, CFS definitional symptoms (i.e.,postexertional malaise lasting more than 24 hours; sore throat; tender neck, or ancillarylymph nodes; muscle pain; multiple joint pain without swelling or redness; headaches ora new type, pattern, or severity; unrefreshing sleep; and impairments in memory or con-centration), other somatic symptoms, and other cognitive symptoms1 on a 100-pointscale, from 0 (no pain or problem) to 100 (severe pain or problem). Definitional symp-toms were taken from the Fukuda et al. (1994) case definition cited previously. In addi-tion, whether each symptom occurred before the onset of severe fatigue and whether thesymptom had lasted for at least 6 months was also assessed. Participants were asked toretrospectively rate the symptoms they experienced during the worst period of their ill-ness, and second, to rate the symptoms they were currently experiencing on the day ofassessment. Dates for the worst period of time were recorded; for the CFS participants,this period lasted more than 6 months (for the control participant, because he was not ill,he filled out this form to conform to a 6-month period one year ago) . In a previous study(Jason et al., 1997), a modified version of this form had high test-retest reliability over a2-week period (test-retest agreement: 76%–92%).

Activity level.All participants were asked to wear a CSA actigraph (Tryon & Williams,1996), programmed to record at 1-minute intervals, on their waists 24 hours a day for 15days except when they bathed. This small, lightweight, cost-efficient device quantifiesmovement intensity into 128 levels and can store data at 1-minute intervals for 22 daysbefore filling memory. Compliance can be checked because not wearing the device cre-

1Using the 100-point rating scale, data were also collected on other somatic symptoms that are frequentlyexperienced by persons with CFS (Bell, 1991; Holmes et al., 1988). These symptoms include racing heart, chestpain, shortness of breath, upset stomach, weight change, dizziness, ringing in the ears, sweating hands, nightsweats, tense muscles, chills or shivering, hot or cold spells, feverish feeling, lowered temperature, tinglingfeeling, paralysis, blurred vision, light sensitivity, blind spots, eye pain, rash, and allergies.Participants also rated on a 100-point severity rating scale additional cognitive difficulties that commonlyafflict individuals with CFS (Bell, 1991; Holmes et al., 1988). They include slowness of thought, absentmind-edness, confusion, reasoning difficulties, forgetting thoughts, difficulty choosing words, difficulty followingthings, difficulty understanding, and slowness to react.


ates a distinctive record of consecutive zeros. All participants complied with the wearinginstructions. The waist was chosen because vertical movements of the waist are stronglyassociated with energy expenditure. Tryon and Williams (1996) demonstrated that theCSA actigraph has excellent within and between device reliability and validity.

RESULTS

Participant 1

Participant 1 is a healthy, 51-year-old White male teacher who is not suffering from CFS.On the Fatigue Scale, developed by Chalder et al. (1993), this control participant obtaineda total score of 5, with a score of 3 for physical symptoms and a score of 2 for mentalsymptoms. Figure 1 shows the eight symptoms contained with the Fukuda et al. (1994)definition, as well as an overall rating of fatigue. Figure 1 shows that even though thecontrol participant is not suffering from any chronic illnesses, he has been experiencinga number of the CFS definitional symptoms for 6 or more months. In fact, using currentassessment procedures (i.e., binary classification), the control participant is close to meet-ing the symptom criteria for CFS (presence of fatigue and three minor symptoms).

However, by having Participant 1 rate the severity of his symptoms, the nature of hiscondition becomes clear. Participant 1 rated his one major symptom, fatigue, and all threeof his minor symptoms as being mild (5 on 100-point scale). Had data only been collectedon symptom occurrence and not symptom severity, Participant 1’s symptom profile wouldhave had many of the characteristics of a person with CFS. Moreover, his symptomsmight have been considered suggestive of serious or chronic illness. Yet when severityratings are obtained for two time points, Participant 1 can be readily distinguished frompersons with CFS2.

Participant 2

This unemployed, 56-year-old, White man reported that he had been suffering from CFSand its related symptoms for approximately the last 20 years. Participant 2 scored 31 onChalder’s (1993) Self-Rating Fatigue Scale, with a physical subset score of 21, and amental subset score of 10. At the time he first became ill, he felt as though he had comedown with a terrible case of the flu within less than 24 hours. During this time, which wasthe worst period of his illness, he was confined to his home and virtually bedridden. Sincethe onset of CFS, his condition has gradually improved over the last 20 years. However,Participant 2 continues to suffer from fatigue and a number of somatic and cognitivesymptoms. He has remained moderately ill in spite of his improvements. Participant 2 ispresently unemployed and on disability due to his illness. He requires approximately 12hours of rest per day, and limits his daily activities to only 2 or 3 hours a day. He reportsthat a full day of activity would “do him in” (i.e., trigger a relapse), and that he is there-fore careful not to overexert himself. Despite his condition and his concerns, overallParticipant 2 has kept a positive attitude.

Figure 1 presents a comparison of Participant 2’s severity ratings for CFS defini-tional symptoms during the worst period of his illness, approximately 20 years ago when

2Participant 1 rated the additional somatic symptoms as not being problems. He rated only one of the additionalcognitive symptoms, absentmindedness, as fairly mild (10). For space consideration, for all three participants,figures illustrating additional somatic and cognitive symptoms are not included in this article. Those who areinterested may request these figures by writing the first author.


Figure 1. Comparison of Participant 1, 2 and 3’s Ratings for CFS Definitional Symptoms Experienced DuringHis Worst Period of Illness and the Day of Assessment.


he first became ill, and the day of data collection. This figure reflects the improvementsthat he reported experiencing over the past 20 years. At the worst period of his illness,Participant 2 rated the majority of the CFS definitional symptoms as having been extremelysevere. At the time of data collection, however, severity levels for definitional symptomshad decreased by 75–85 points.

Compared to Participant 1, Participant 2’s symptom profile differs considerably.Participant 2’s fatigue levels are five times higher than Participant 1’s, and four of Par-ticipant 2’s minor symptoms (i.e., postexertional malaise lasting more than 24 hours,tender neck or ancillary lymph nodes, unrefreshing sleep, and impairments in memory orconcentration) are two to three times as severe as Participant 1’s. Had we only collecteddata on symptom occurrence, these meaningful differences would not have been observed.Participant 1’s and Participant 2’s severity ratings for CFS definitional symptoms duringthe worst period of illness are also markedly different. Because Participant 1 has neverbeen chronically ill, his ratings for the worst period of illness were the same as the day ofdata collection. For Participant 2, however, ratings for the worst period of illness weresevere. As a result, these two individuals’ symptom profiles are distinct over time anddistinguish Participant 1 from Participant 2.3

Participant 3

Participant 3 is a 47-year-old retired, White woman who first became ill with CFS 5½years ago. Her illness began with an infection that she acquired in the hospital afterundergoing a surgical procedure. She reported that this period was the worst period of herillness; as a result of her condition, she was forced to retire early from her job as aninformation systems’ consultant. On the Fatigue Scale, Participant 3 scored 30, with aphysical subscore of 21, and a mental subscore of 9. During the first 3 years of her illness,Participant 3 reported that she was completely “wiped out”. She estimated that duringthose three years her capacity to function was impaired by 95%. After her third year ofbeing ill, she began to experience some relief from her symptoms. In the past 22 years shehas slowly improved to the point where she now feels that her capacity to function isimpaired by 70%. She presently is able to function for about 8 hours a day; however, sherequires rest periods throughout the day. For example, if she pushes herself through theentire morning without resting, she becomes exhausted and has to spend the remainder ofthe day in bed.

Figure 1 presents comparisons of Participant 3’s severity ratings for CFS definitionalsymptoms during the worst period of her illness, approximately 5½ years ago, and theday of data collection. During the worst period of her illness, Participant 3 reported thatshe had been impaired overall by 95%, and she rated her CFS definitional symptoms ashaving been extremely severe. At the time of data collection, when she reported that shewas 70% impaired, Participant 3 rated a number of her CFS definitional symptoms as less

3In respect to Participant 2’s additional somatic and cognitive symptoms, at the worst period of his illness,Participant 2 rated the majority of his cognitive symptoms as having been extremely severe, and a number ofthe somatic symptoms as problematic. At the time of data collection, however, severity levels for cognitivesymptoms had decreased by 95–90 points, and the majority of his somatic symptoms were no longer rated asproblematic. During his worst period, Participant 2 suffered from 21 different somatic symptoms. On the day ofdata collection, however, he only reported four somatic symptoms that were of mild severity. These findings areconsistent with Participant 2’s self-reported improvements in symptomatology.


severe. Figure 1 shows the modest improvements Participant 3 experienced in symptomseverity for CFS definitional symptoms.4

Compared to Participant 1 (control participant), Participant 3 has a strikingly differ-ent symptom profile. Participant 3’s symptom profile is marked by high severity andchronicity. The data charted in Figure 1 clearly differentiate a person with CFS fromhealthy individuals who commonly experience a number of the defining symptoms ofCFS.

Actigraph Data

Table 1 presents ANOVA results for the 15 days of actigraph data on the three partici-pants. The standard deviation was included as a measure of variation. It is a standarddeviation over the 60, 1-minute measurements taken during each hour. We used thismeasure because we believe that the ability to go from low to high activity is morereflective of CFS than is absolute activity level. Hence, we use the standard deviation toquantify activity variability on an hourly basis. Analysis of variance revealed significanteffects for the means for time and time3 person; for the standard deviation, there was asignificant effect for time, person, and time3 person.

In Table 2, each 24-hour day was divided into three phases: Hours 1–8, Hours 9–16,and Hours 17–24. These periods of time cover early morning hours (1–8 a.m.), morningand early afternoon (9 a.m.–4 p.m.) and evening hours (5 p.m.–12 a.m.). These are threedescriptive time blocks that were equally relevant across the three participants. Usinganalysis of variance, there was a significant difference across the three participants foreach of the time periods, using either mean (M) or standard deviation scores. Using theTukey method, for the mean and standard deviation score, Participant 2 (S.D.) was sig-nificantly different from Participant 1 during the first two time periods. Participant 3 wassignificantly different from Participant 1 only during the first time period, using meanscores, but for all three time periods using standard deviations.

Figure 2 presents the three participants’ standard deviation scores across the 15 days.5

Participant 1 had regular patterns of activity, with high levels of variability during the day

4Participant 3’s additional somatic and cognitive symptoms are discussed later. The majority of improvementsParticipant 3 experienced were in her somatic and cognitive symptoms. During the worst period of her illness,she had rated all of the additional cognitive symptoms as extremely severe (100 to 90 on a scale of 100), and allbut two of the other somatic symptoms (paralysis and rash) as having been moderately to extremely severe. Atthe time of data collection, when she reported that she was 70% impaired, Participant 3 rated a number of hersomatic and cognitive symptoms as less severe. For example, somatic symptoms such as blurred vision, ringingin the ears, shortness of breath, chest pain, dizziness, abnormal sensitivity to light, and racing heart all decreasedin severity substantially (by approximately 50 to 30 points). In addition, all of Participant 3’s cognitive symp-toms decreased by 25 to 40 points, with levels of confusion decreasing the most. Levels of confusion wereoriginally rated as being extremely severe, 90 on the 100-point scale, yet on the day of data collection, thissymptom was only rated as moderately severe (50).5A figure showing the means can be obtained by writing the first author.

Table 1. ANOVA Results for the Actigraph Data

Time Person Time 3 Person

M <.001 .57 <.002SD <.001 <.001 <.001


and low levels at night. The data for Participant 1 in Figure 2 indicates the hour to hourvariability and wider activity fluctuations during the daytime were observed more inParticipant 1 than in Participants 2 and 3. Participants 2 and 3 have less clearly definedpatterns of high variability during the day and low variability at night.

DISCUSSION

CFS is presently defined primarily by the presence of severe, debilitating fatigue and theconcurrent occurrence of various symptoms (Fukuda et al., 1994). Given the importanceof these symptoms in defining and diagnosing CFS, assessment of the minor symptomcriteria requires measures that provide descriptive clinical data and capture the symptomdynamics involved in CFS. In addition, because CFS might be a heterogeneous diseasesyndrome, subsuming distinct subsets of patients (Friedberg, Mackenzie, Dechene, &Fontanetta, 1994; Hickie et al., 1995; Holmes, 1991), instruments need to be sensitiveenough to differentiate these distinct subsets of CFS patients.

Yet despite the importance of symptoms in defining CFS and the need to differenti-ate distinct subsets of patients, the majority of current measures used to the assess CFSare lacking in sophistication and sensitivity. The present study illustrates the types of datathat can be obtained through the use of a more differentiated assessment system. Byhaving patients rate the severity of their symptoms on a continuum for two time points,quantitative data that reflect the complexities and dynamics of CFS symptomatology canbe obtained easily in one assessment session.

Many patients with CFS have symptoms for extended periods of time, but because ofimprecise wordings of the binary symptoms some individuals with CFS are not scored ashaving a symptom when they really do have it. For example, one minor symptom ispostexertional malaise lasting more than 24 hours. Some patients do not endorse this itembecause they have postexertional malaise for only for 2–5 hours. So when they are askedif they are severely fatigued after exercise, they answer affirmatively, but not when theyare asked if the postexertional malaise lasts more than 24 hours. In addition, some patientshave limited all types of exercise, so they rarely experience this item, but they would ifthey did exercise. This is a clear example where patients who do have this exerciseintolerance symptom are not accurately captured by assessments using the current casedefinition of CFS.

Although the self-rating system presented in this study is partially confounded byhaving participants retrospectively rate their symptoms for the worst period of their ill-

Table 2. Mean and Standard Error of the Mean for Two Dependent Variables

Participant2

Participant3

Participant1 p 2 vs. 3 1 vs. 2 1 vs. 3

M1–8 56 (7.7) 75 (7.7) 25 (8.4) <.0001 — * *

9–16 181 (24) 239 (23) 279 (23) .01 — * —17–24 273 (27) 175 (27) 241 (27) .03 * — —

SD1–8 113 (10) 151 (10) 64 (11) <.0001 * * *

9–16 307 (27) 327 (26) 529 (26) <.0001 — * *

17–24 410 (26) 269 (26) 397 (26) <.0001 * — *

*indicates statistical significance by Tukey’s method.


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ness, there are still several advantages to this approach. As demonstrated by the threeCFS case studies, this system is able to capture both the intrapersonal and interpersonalvariability of CFS. By charting symptom patterns, changes in patients’ symptoms can beobserved over time, and such changes can be used to track progress. In addition, bycharting symptoms, patients’ symptom patterns can also be compared with one another.

The first case study was included for comparative purposes. It is clear from Partici-pant 1’s symptom ratings that he actually has several of the critical case definition symp-toms, even though at a minimal level. These symptoms are common in the generalpopulation; however, it is not common when such symptoms remain severe for longperiods of time. In contrast to the participants with CFS, Participant 1’s symptoms wereextremely mild. As we argue throughout this article, when dealing with CFS samplesthere is a need to assess levels of symptom severity rather than just symptom occurrencealone. In future research, when using healthy controls as a matched group, ratings for theworst period of time should be the same time interval over which one of the index caseshad CFS.

The second case study presented clearly illustrated the fluctuating nature of thisillness. Dramatic improvements were reported by Participant 2 for psychological, neuro-psychological, and somatic symptomatology. It is important to note that, despite his markedimprovement, Participant 2 continued to experience a number of symptoms and stillqualified for the diagnosis of CFS. Health care providers and caregivers cannot assumethat marked reductions in symptomatology are indicative of recovery. As demonstratedby Participant 2, even when significant improvements are obtained, a number of symp-toms may persist at substantial levels. Thus, although such patients may appear to feelbetter, these individuals are still considerably impaired by CFS.

The third case study presented provides an entirely different clinical picture, dem-onstrating the interpersonal variability of CFS. In contrast to Participant 2, Participant 3reported experiencing only slight reductions in CFS definitional symptoms. By chartingher symptom pattern, it is apparent that many areas of functioning continue to be affectedby CFS. Participant 3 did, however, experience notable reductions in a number of herother somatic and cognitive symptoms. These small improvements may represent thebeginning of a slow pattern of recovery that is typical to CFS (Bell, 1991). In theseregards, this charting system can be used to provide positive feedback to patients whoexperience reductions in their symptoms over time.

The actigraph data show clear differences between the healthy control participantand the two participants with CFS. In general, for the participants with CFS, there werefewer time periods of more variable activity, which was evident for Participant 1. Par-ticipant 2, who had made a partial recovery, had patterning that more closely resembledParticipant 1, whereas Participant 3’s activity, which was reported to be the most impaired,indicated the highest level of disruption of patterns of activity during the day and of restat night. It is possible that the actigraph might be a useful tool to gather activity on dailypatterning of activity, and improvements might reflect more regular patterning as evidentin Participant 1.

A study by Fry and Martin (1996) examined measures of activity for children withCFS and healthy controls. When an objective measure of activity averaged over 3 dayswas examined, there were no significant differences between the two groups. They exam-ined only differences among the individuals, not differences over time, person by timeinteractions, or measures of variability. Looking at overall daily levels of activity mightbe misleading, as it may be the pattern of activity over time and its variability that is mostimportant in differentiating people with CFS from controls. In the present study, theoverall mean differences among participants when examining just the person factor were


not significantly different, but there were significant mean differences when examiningtime and interaction effects, as well as when examining a measure of variability. In addi-tion, Fry and Martin (1996) apparently dichotomized continuous activity data into activeand inactive epochs, calculated the percentage of active epochs, and found no differ-ences. Such a procedure is questionable on several grounds. First, no criteria of “active”were given. The statistical results are probably sensitive to the cut point between activeand inactive. One always loses statistical power through dichotomization. The GaewilerElectronic Activity Monitor is not proportional to intensity of movement. In addition, Fryand Martin’s data do indicate that child and parent activity ratings seem to severelyunderreport periods of activity, which questions whether these types of data are reliable.

Another study by Vercoulen et al. (1997) found that patients with CFS and those withmultiple sclerosis (MS) had similar activity levels, as measured by an Actometer, andboth groups were significantly less active than healthy participants. However, only in theCFS group were low levels of activity related to fatigue, and patients with CFS hadsignificantly higher scores on activity-related fatigue expectations than those with MS.These findings suggest that there are important differences between the patients withCFS and MS, even though they both have low levels of activity. Although none of theself-report measures had a strong correlation with the Actometer in Vercoulen et al.’sstudy, the less the self-report instrument required general subjective interpretations, themore the instrument was related to the Actometer.

There are several limitations in this study. First, there is a need to replicate thefindings in this study with larger samples. The reliability of the CFS Symptom RatingForm needs to be established for non-CFS patients, as well as for CFS patients. In addi-tion, normative data needs to be provided to assess the clinical meaning of the patient’sratings. Finally, if this scale is to be used for retrospective reports, then its validity for thispurpose must be established. Future research also needs to address whether sources ofsymptom variability might reside in disease pathophysiology, the presence of other comor-bidities, patient mood, and daily stress.

The nature and diagnosis of CFS is a very important research problem. Presently,there is no definitive way of deciding who has it and who does not, and so the clinicalutility of any assessment or diagnostic instrument will be limited in its reliability. Toimprove the diagnostic criteria, studies are needed that will require hundreds of patients,and include normal, medical, and psychiatric control groups. These studies will need toemploy factor and cluster analyses to reveal symptom patterns and patient groupings, andthese results could be used to determine whether a diagnostic entity is distinct from otherknown entities, and whether it is homogeneous or contains distinct subgroups.

Future definitions of CFS may need to include specific guidelines pertaining to theimportance of symptom severity in the diagnostic procedure. Given the high variabilityin symptom severity among persons with CFS, health care professionals may need astandardized procedure for determining whether or not a particular symptom is severeenough to qualify as one of the four minor symptoms required for the diagnosis of CFS.Presently, there are no guidelines for physicians to follow when determining whether asymptom is severe enough to qualify as meeting the diagnostic criteria. If CFS is to bediagnosed reliably across health care professionals, we recommend the establishment ofcutoffs points at which symptoms are considered to be severe enough to meet the casedefinition for CFS.

Without such standardization, symptom variability will be a function of the assess-ment procedure and etiological factors. If health care professionals are to improve theirunderstanding of the complexities of this disease and their ability to identify distinctsubtypes of CFS patients, the current U.S. case definition may need to be revised to


clarify the significance of symptom severity in diagnostic and assessment procedures(Jason, Richman, et al., 1997).

This study has direct significance to the field of clinical psychology. Prevalenceestimates of CFS have ranged from 4 to 2,600 per 100,000 (Jason, Ropacki, et al., 1997),and these vastly different estimates might in part be due to ambiguities in the differentcase definitions. This imprecision contributes to difficulties in directly comparing sam-ples in assessment and treatment studies, as they might be capturing very different typesof patients. It is important to develop strategies for better defining symptoms of CFS, andsuch work will ultimately contribute to a next generation of more precise and sophisti-cated assessments so that clinicians and scientists will be better able to assess and treatindividuals with this syndrome.

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chronic fatigue syndrome: assessing symptoms and activity level

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