The Development of a Revised Canadian Myalgic Encephalomyelitis Chronic Fatigue Syndrome Case Definition

Abstract

Problem statement: Several investigators have indicated that case definitions for Chronic Fatigue Syndrome (CFS) are characterized by vaguely worded criteria that lack operational definitions and guidelines. The most widely used CFS case definition is the Fukuda et al. criteria, which uses polythetic criteria (i.e., patients are only required to have four out of a possible eight symptoms). Yet two of these eight symptoms (post-exertional malaise and memory/concentration problems) are an essential feature of this illness and the Fukuda et al. criteria do not require that these symptoms be present among all patients. Significant methodological problems could occur if investigators in different settings recruit samples with different percentages of these core symptoms. In contrast, the Canadian clinical case definition does require specific ME/CFS symptoms such as post-exertional malaise and memory/concentration problems. The provision of operationally explicit, objective criteria on specific key symptoms might reduce criterion variance as a source of unreliability. In addition, the use of structured interview schedules will ensure that symptoms are assessed in a consistent way across settings. Conclusion/Recommendations: In this article, we specified explicit rules for determining whether critical symptoms meet ME/CFS criteria using a revised Canadian case definition and a questionnaire has been developed to assess core symptoms. It is hoped that these developments will lead to increased reliability of this revised Canadian case definition as well as more frequent use of these criteria by investigators.

Characterising eye movement dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome

“…In this context, blur may indeed offer an explanation for our findings. Individuals with ME/CFS often report that they experience a number of symptoms related to blurred vision [18] to the extent that being 'unable to focus vision' has been incorporated into some diagnostic measures of the condition [21]. As a consequence, the red circle may have appeared more 'blurry' to patients than to controls, deleteriously affecting their ability to accurately track it as it moved across the screen.…”

“…All of the patients reported that they had been given a diagnosis of ME/CFS by a medical practitioner. Before being admitted to the study, they completed the DePaul Symptom Questionnaire [21] which is a useful screening tool recently developed to assess for ME/CFS. Using this tool, it could be ascertained whether patients fulfilled the standard CDC Definition [8], the Canadian ME/CFS Case Definition [5], or the International Consensus ME Case Definition [6].…”

Increased Vulnerability to Pattern-Related Visual Stress in Myalgic Encephalomyelitis

“…All patients had an ME/CFS diagnosis, confirmed using the DePaul Symptom Questionnaire (Jason et al, 2010). Participants had no history of eye disease and acuity was within the normal range.…”

Listen to the Story: Chronic Fatigue Syndrome Patients Do Not Live in a Vacuum

“…Therefore, some assert that the CDC criteria may fail to detect patients with 'myalgic encephalomyelitis', considered to be a 'neurological' illness and distinguished from chronic fatigue with a 'psychiatric' background [6,11] . However, such an alleged dichotomy would be superfluous if clinicians did not only 'count symptoms' to diagnose CFS, but also paid attention to contextual factors.…”

“…Or a women who grew up with a violent, alcoholic father developed CFS following a whiplash injury while being stalked by her ex-partner. Again, by fully appreciating the narrative of a patient's illness, the abovementioned dichotomy [6,11] may prove to be futile. Consistent with this view, patients attending a 'psychologically' and 'biomedically' oriented CFS center, respectively, showed no major differences in psychopathology [15] .…”