Category: Case Definition

Chronic fatigue syndrome. …and study them separately

Comment on: Chronic fatigue syndrome: prevalence and outcome. [BMJ. 1994]

 

Editor,-The struggle over myalgic encephalomyelitis and the chronic fatigue syndrome is not, as S M Lawrie and A J Pelosi suggest, whether they are physical or mental illnesses. Both sides in this debate accept that most illnesses combine organic and psychological factors. The struggle is about methodology and definition and, in particular, how different methodologies and definitions inevitably lead to different findings on the degree to which depression is a perpetuating agent in these conditions.

One side favours studying the chronic fatigue syndrome as a single entity, arguing that there is insufficient knowledge at present to differentiate between different chronic fatigue syndromes. This side prefers Sharpe et al’s broad definition of the syndrome, which includes depressive illness, anxiety disorders, and the hyperventilation syndrome.2 Unsurprisingly, studies that use these criteria find higher levels of depression ) or “psychosocial disorders”-yet another woolly term).

The other side argues that there is sufficient knowledge to distinguish specific chronic fatigue syndromes, particularly the much studied myalgic encephalomyelitis, and that it must be better science in these cases to study such syndromes in their own right. Furthermore, it argues that the study groups used in research based on broadbrush criteria will have been so aetiologically heterogeneous as to invalidate the findings. This side, which includes the national patient organisations, equates myalgic encephalomyelitis with Holmes et als tighter definition of the chronic fatigue syndrome, which focuses more on organic symptoms and, again unsurprisingly, finds lower levels of depression similar to those found in patients with cancer and multiple sclerosis-that is, the levels that might be predicted in any chronic illness.3

You can read the rest of this comment here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2540172/pdf/bmj00440-0054a.pdf

 

Source: Anderson N. Chronic fatigue syndrome. …and study them separately. BMJ. 1994 May 14;308(6939):1298. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2540172/

 

Chronic fatigue syndrome. Distinguish between syndromes…

Comment in: Chronic fatigue syndrome and myalgic encephalomyelitis. [BMJ. 1994]

Comment on: Longitudinal study of outcome of chronic fatigue syndrome. [BMJ. 1994]

 

EDITOR,-I note that several people writing in the BMY are still confusing myalgic encephalomyelitis with the chronic fatigue syndrome. I wish to clarify matters. From a scientist’s point of view, the main problem is not the term chronic fatigue syndrome but the various diagnostic criteria that go with it. For instance, the strict Australian definition adopted by Wilson et al is similar to that for myalgic encephalomyelitis.2 As a result, it is reasonably certain that in this article the two names probably refer to the same disease.

The “Oxford” criteria used in Britain, however, are far broader, covering all patients whose severe, unexplained fatigue has been present for at least half of the time and for at least six months. The only other requirements are that the fatigue must have had a definite onset and that it affects both physical and mental functioning. Unlike with the strict Australian definition, no immunological criteria have to be met.2 Moreover, there do not have to be appreciable fluctuations in symptoms still a major criterion for myalgic encephalomyelitis.

In terms of prevalence, a recent study found that 17 of 686 (2-5%) attenders in general practice fulfilled the Oxford criteria for the chronic fatigue syndrome.3 When a further four patients who did not meet the criterion of a definite onset were also included the estimated prevalence increased to 3%. In contrast, the prevalence of myalgic encephalomyelitis rarely exceeds 1-5 per 1000.4

Most patients who fulfil the Oxford criteria suffer not from myalgic encephalomyelitis but from more common conditions, notably depression, anxiety states, sleep disorders, and fibromyalgia. None of these disorders occur in epidemics …

You can read the rest of this comment here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2540201/pdf/bmj00440-0053c.pdf

 

Source: Goudsmit EM. Chronic fatigue syndrome. Distinguish between syndromes… BMJ. 1994 May 14;308(6939):1297-8. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2540201/

 

A comparison of case definitions of chronic fatigue syndrome

Abstract:

We compared three case definitions of chronic fatigue syndrome (CFS) applied to patients followed in CFS clinics at two institutions. All patients had debilitating fatigue without apparent etiology; patients with medical conditions associated with chronic fatigue and with major psychiatric disorders were stratified and presented separately. Patients were classified according to whether they met case definitions developed by a Centers for Disease Control and Prevention (CDC) Working Group, a British group, or an Australian group. When findings for 805 patients followed at the two clinics were combined, 61% met the CDC criteria, 55% met the British criteria, and 56% met the Australian criteria; these proportions were relatively similar at both sites. In addition, similar laboratory abnormalities were found for all case groups and for fatigued patients who met none of the three case definitions. These data suggest that more inclusive case definitions may be superior.

 

Source: Bates DW, Buchwald D, Lee J, Kith P, Doolittle TH, Umali P, Komaroff AL. A comparison of case definitions of chronic fatigue syndrome. Clin Infect Dis. 1994 Jan;18 Suppl 1:S11-5. http://www.ncbi.nlm.nih.gov/pubmed/8148436

 

Prevalence of fatigue and chronic fatigue syndrome in a primary care practice

Abstract:

BACKGROUND: Our goals were to determine the prevalence of unusual, debilitating fatigue and the frequency with which it was associated with the chronic fatigue syndrome (CFS) or other physical or psychological illness in an outpatient clinic population.

METHODS: We prospectively evaluated a cohort of 1000 consecutive patients in a primary care clinic in an urban, hospital-based general medicine practice. The study protocol included a detailed history, physical examination, and laboratory and psychiatric testing.

RESULTS: Five patients who came because of CFS studies were excluded. Of the remaining 995, 323 reported fatigue, and 271 (27%) complained of at least 6 months of unusual fatigue that interfered with their daily lives. Of the 271, self-report or record review revealed a medical or psychiatric condition that could have explained the fatigue in 186 (69%). Thus, 85 (8.5%) of 995 patients had a debilitating fatigue of at least 6 months’ duration, without apparent cause. Of these patients, 48 refused further evaluation, and 11 were unavailable for follow-up; 26 completed the protocol. Three of the 26 were hypothyroid, and one had a major psychiatric disorder. Of the remaining 22 patients, three met Centers for Disease Control and Prevention criteria for CFS, four met British criteria, and 10 met the Australian case definition. The point prevalences of CFS were thus 0.3% (95% confidence interval [CI], 0% to 0.6%), 0.4% (95% CI, 0% to 0.8%), and 1.0% (95% CI, 0.4% to 1.6%) using the Centers for Disease Control and Prevention, British, and Australian case definitions, respectively. These estimates were conservative, because they assumed that none of the patients who refused evaluation or were unavailable for follow-up would meet criteria for CFS.

CONCLUSIONS: While chronic, debilitating fatigue is common in medical outpatients, CFS is relatively uncommon. Prevalence depends substantially on the case definition used.

 

Source: Bates DW, Schmitt W, Buchwald D, Ware NC, Lee J, Thoyer E, Kornish RJ, Komaroff AL. Prevalence of fatigue and chronic fatigue syndrome in a primary care practice. Arch Intern Med. 1993 Dec 27;153(24):2759-65. http://www.ncbi.nlm.nih.gov/pubmed/8257251

 

The chronic fatigue syndrome

Sir, Although many doctors equate chronic fatigue syndrome (Oxford definition) with what we call myalgic encephalomyelitis (ME), there are some noteworthy differences.

Firstly, in Britain, chronic fatigue syndrome is an umbrella term covering a number of different conditions including neurasthenia, effort syndrome and fibromyalgia. ME is a more specific entity (see the ‘ 10, 1992) and unlike the above, has been closely linked to a persistent infection and immune system activation.

Secondly, while profound fatigue is undeniably the most common symptom of ME, it is rather different from the type of tiredness which people normally experience after exertion. For example, it is often accompanied by feelings of illness which are so unlike anything which people have had before that patients frequently say they cannot describe it. Some have referred to the latter as a severe ‘flu-like’ malaise, others have likened it to being poisoned. Regrettably, having subsumed ME under a general heading of chronic fatigue syndrome, this important and disabling aspect of ME will almost certainly be overlooked.

You can read the rest of this letter here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2399627/pdf/postmedj00050-0083a.pdf

 

Source: Macintyre A, Hume MC. The chronic fatigue syndrome. Postgrad Med J. 1993 Feb;69(808):164. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2399627/

 

Diagnostic criteria for chronic fatigue syndrome by the CFS Study Group in Japan

Abstract:

Much interest recently has been given to chronic fatigue syndrome (CFS) in Japan as other countries. The CFS Study Group sponsored by the Ministry of Health and Welfare has been developed since April 1991, A diagnostic criteria for CFS was newly proposed by this group. The criteria is substantially based upon the working case definition, which was made by Holmes and colleagues in 1988. There are some modification from CDC working case definition; the criteria of probable cases of CFS was defined, and postinfectious CFS was also given.

 

Source: Kitani T, Kuratsune H, Yamaguchi K. Diagnostic criteria for chronic fatigue syndrome by the CFS Study Group in Japan. Nihon Rinsho. 1992 Nov;50(11):2600-5. [Article in Japanese] http://www.ncbi.nlm.nih.gov/pubmed/1287236

 

Definition of the chronic fatigue syndrome and its issues

Abstract:

This article reviewed Definition of CFS proposed by CDC 1988. There are several issues in Definition for CFS of CDC. It is presented that other chronic clinical conditions have been satisfactorily excluded, including preexisting psychiatric diseases in (2) of major criteria.

However, fibromyalgia can not be excluded from the fifth symptom of minor criteria, myalgia, and also depression from the ninth symptom.

It is practically difficult to define impairment of average daily activity below 50% of the patient’s premorbid activity level for a period of at least 6 months, as shown in (1) of major criteria, and it is not adapted for a first visit patient.

Definition for CFS of CDC has been discussed on EBV infection, but not written on postviral fatigue syndrome and myalgic encephalomyelitis. Especially whether epidemic type of CFS is present or not was not discussed. Diagnostic criteria of CFS is necessary for clinical practice.

 

Source: Hashimoto N. Definition of the chronic fatigue syndrome and its issues. Nihon Rinsho. 1992 Nov;50(11):2591-9. [Article in Japanese] http://www.ncbi.nlm.nih.gov/pubmed/1287235

 

NIH conference. Chronic fatigue syndrome research. Definition and medical outcome assessment

Abstract:

A workshop was held 18 to 19 March 1991 at the National Institutes of Health to address critical issues in research concerning the chronic fatigue syndrome (CFS). Case definition, confounding diagnoses, and medical outcome assessment by laboratory and other means were considered from the perspectives of key medical specialties involved in CFS research.

It was recommended that published Centers for Disease Control (CDC) case-definition criteria be modified to exclude fewer patients from analysis because of a history of psychiatric disorder. Specific recommendations were made concerning the inclusion or exclusion of other major confounding diagnoses, and a standard panel of laboratory tests was specified for initial patient evaluation.

The workshop emphasized the importance of recognizing other conditions that could explain the patient’s symptoms and that may be treatable. It was viewed as essential for the investigator to screen for psychiatric disorder using a combination of self-report instruments followed by at least one structured interview to identify patients who should be excluded from studies or considered as a separate subgroup in data analysis.

Because CFS is not a homogeneous abnormality and because there is no single pathogenic mechanism, research progress may depend upon delineation of these and other patient subgroups for separate data analysis. Despite preliminary data, no physical finding or laboratory test was deemed confirmatory of the diagnosis of CFS.

For assessment of clinical status, investigators must rely on the use of standardized instruments for patient self-reporting of fatigue, mood disturbance, functional status, sleep disorder, global well-being, and pain. Further research is needed to develop better instruments for quantifying these domains in patients with CFS.

 

Source: Schluederberg A, Straus SE, Peterson P, Blumenthal S, Komaroff AL, Spring SB, Landay A, Buchwald D. NIH conference. Chronic fatigue syndrome research. Definition and medical outcome assessment. Ann Intern Med. 1992 Aug 15;117(4):325-31. http://www.ncbi.nlm.nih.gov/pubmed/1322076

 

Chronic fatigue syndrome criteria. A critique of the requirement for multiple physical complaints

Abstract:

OBJECTIVE: The purpose of this study was to test the hypothesis that the patients with chronic fatigue who have the highest number of medically unexplained physical symptoms over their lifetime would also have the highest prevalence of current and lifetime affective and anxiety disorders, lifetime affective symptoms, and the most functional disability. A further goal was to use this information to modify the current case definition to better identify a subgroup of patients with chronic fatigue syndrome who are less likely to have psychiatric illness.

DESIGN: Two hundred eighty-five consecutive patients with chronic fatigue were interviewed with the National Institute of Mental Health Diagnostic Interview Schedule and completed four self-rating questionnaires measuring psychologic distress, functional disability, and the tendency to amplify symptoms. Based on previously published data, patients were divided into four groups with a progressively higher number of lifetime medically unexplained physical symptoms. The prevalence of current and lifetime psychiatric disorders, lifetime psychologic symptoms, and extent of functional impairment was then compared in these four groups of patients.

MAIN RESULTS: The prevalence of current and lifetime psychiatric diagnosis and lifetime depressive symptoms increased linearly with the number of lifetime physical symptoms that the patient experienced. The extent of impairment in activities of daily living and the tendency to amplify symptoms also increased linearly with the number of medically unexplained physical symptoms.

CONCLUSION: The patients with the highest numbers of medically unexplained physical symptoms had extraordinarily high rates of current and lifetime psychiatric disorders. These data suggest that the current case definition for chronic fatigue syndrome inadvertently selects for patients with the highest prevalence of lifetime psychiatric diagnoses. A recommendation based on these results is to modify the case criteria for chronic fatigue syndrome to include patients with fatigue and few physical symptoms and to identify and consider excluding patients with high numbers of physical complaints.

Comment in: Defining the chronic fatigue syndrome. [Arch Intern Med. 1992]

 

Source: Katon W, Russo J. Chronic fatigue syndrome criteria. A critique of the requirement for multiple physical complaints. Arch Intern Med. 1992 Aug;152(8):1604-9. http://www.ncbi.nlm.nih.gov/pubmed/1497394

 

Psychiatric illness in patients with chronic fatigue and those with rheumatoid arthritis

Abstract

OBJECTIVES: To identify psychiatric differences between patients with chronic fatigue and those with rheumatoid arthritis and to investigate whether patients meeting Centers for Disease Control (CDC) criteria for chronic fatigue syndrome (CFS) can be differentiated from patients with chronic fatigue on measures of disability and psychosocial distress.

DESIGN: Cross-sectional study comparing 98 patients with chronic fatigue with 31 patients with rheumatoid arthritis on structured psychiatric interviews and patient questionnaires. Nineteen patients meeting CDC criteria for CFS were compared with 79 patients with chronic fatigue not meeting CDC criteria on questionnaires measuring disability and psychosocial distress.

SETTING: Consecutive patients with chronic fatigue were selected from a chronic fatigue clinic at the University of Washington, and 31 consecutive patients with rheumatoid arthritis were sampled from a private rheumatology practice.

MAIN RESULTS: Patients with chronic fatigue had a significantly higher prevalence of lifetime major depression and somatization disorder than did patients with rheumatoid arthritis. Patients with chronic fatigue also had a significantly higher prevalence of current and lifetime psychiatric diagnoses. Only 19 of 98 patients with chronic fatigue met CDC criteria for CFS. Patients meeting CDC criteria for CFS could not be differentiated from the larger group of patients with chronic fatigue on any study variable.

CONCLUSIONS: Patients with chronic fatigue have a significantly higher burden of psychiatric illness than do patients with rheumatoid arthritis. The psychiatric illness preceded the development of chronic fatigue in over half the patients. Centers for Disease Control criteria for CFS did not select a subset of chronic fatigue patients who could be differentiated on disability or psychosocial parameters from patients with chronic fatigue who did not meet CDC criteria.

Comment in The trouble with chronic fatigue. [J Gen Intern Med. 1991]

 

Source: Katon WJ, Buchwald DS, Simon GE, Russo JE, Mease PJ. Psychiatric illness in patients with chronic fatigue and those with rheumatoid arthritis. J Gen Intern Med. 1991 Jul-Aug;6(4):277-85. http://www.ncbi.nlm.nih.gov/pubmed/1890495