A Comparison of Case Definitions for Myalgic Encephalomyelitis and Chronic Fatigue Syndrome

[Dolphin]

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A Comparison of Case Definitions for Myalgic Encephalomyelitis and Chronic Fatigue Syndrome

Madison Sunnquist, Leonard A. Jason, Pamela Nehrke, and Ellen M. Goudsmit

Journal of Chronic Diseases and Management

Submitted: 07 April 2017
Accepted: 16 May 2017
Published: 21 May 2017


Abstract


Many professionals have described the clinical presentation of myalgic encephalomyelitis (ME), but recent efforts have focused on the development of ME criteria that can be reliably applied.

The current study compared the symptoms and functioning of individuals who met the newly-developed Institute of Medicine (IOM) clinical criteria to a revised version of the London criteria for ME.

While 76% of a sample diagnosed with chronic fatigue syndrome (CFS) met the IOM criteria, 44% met the revised London criteria.

The revised London criteria identified patients with greater physical impairment.

The results of this study indicate the need for a standard case definition with specific guidelines for operationalization.

The application of case definitions has important implications for the number of individuals identified with ME, the pattern of symptoms experienced by these individuals, and the severity of their symptoms and functional limitations.

Sample heterogeneity across research studies hinders researchers from replicating findings and impedes the search for biological markers and effective treatments.

 

[hixxy]

The London criteria eliminates everyone that doesn't have viral onset so of course it's going to be more narrow.

 

[Dolphin]

London criteria for ME:

To operationalize the revised London criteria for ME [4], its first author (E.G.) reviewed the DSQ and identified scoring rules.

To meet these criteria, participants needed to have symptoms from the following domains: muscle fatigue / post-exertional malaise, central nervous system involvement, and circulatory impairment.

To demonstrate post-exertional malaise, participants needed to report that their symptoms worsen after minimal physical effort or endorse that one of the following occurs all of the time and is of at least moderate severity: next-day soreness or fatigue after non-strenuous, everyday activities, minimum exercise makes you physically tired, or physically drained or sick after mild activity.

To demonstrate central nervous system involvement, participants needed to indicate that they experience one of the following symptoms all of the time at mild severity or greater: problems remembering things, difficulty paying attention for a long period of time, difficulty finding the right word to say or expressing thoughts, difficulty understanding things, only able to focus on one thing at a time, unable to focus vision or attention, loss of depth perception, absent-mindedness or forgetfulness, feeling unsteady on your feet, or dizziness or fainting.

Finally, to demonstrate circulatory impairment, participants needed to indicate that they experience one of the following symptoms all of the time at mild severity or greater: cold limbs, feeling chills or shivers, feeling hot or cold for no reason, feeling like you have a high temperature, feeling like you have a low temperature, or having intolerance to extremes of temperatures.

Individuals with medical or psychiatric diagnoses that could explain these symptoms were excluded from analysis.

I find it hard to understand why one type of symptom has to be of at least moderate severity while other types of symptom only have to be of mild severity.

I'm left wondering whether these thresholds might have been decided after looking at the data.

Leonard Jason based on past experience uses "of at least moderate severity" when he is operationalising criteria but in this case they said the decision was made by Ellen Goudsmit.

They are free if they want to use the threshold "all of the time" for the symptoms but Leonard Jason doesn't use this for his other criteria. I remain to be convinced it is the best way to define ME and so am not confident that the data in this study is in any way definitive.

The authors themselves say:

While 75% of participants met the IOM criteria, 44% met the revised London criteria. The revised London case definition likely selected fewer participants due to the higher frequency thresholds for required symptoms.

 

[Dolphin]

Individuals in the IOM group were significantly older than those in the London-Revised group [F (1, 1001) = 4.74, p= 0.03]. Additionally, individuals in the IOM group had obtained higher levels of education than those in the London-Revised group [χ2 (5, N = 997) = 15.01, p= 0.01].

I remain to be convinced that these differences are that reliable and instead could be due to the different thresholds use for the two criteria as I mentioned in the last comment.

 

[Dolphin]

Some limitations the authors mention:

An important limitation of the current study is that the DSQ was not specifically developed to assess the symptoms of the revised London criteria [24]. The DSQ was recently updated to include items that better assesses the London criteria; however, when the current samples were collected, this revised instrument was not available. Thus, caution should be exercised in interpreting the current study; validity challenges can be introduced when criteria are assessed using instruments not originally intended to measure them [25]. An additional limitation of this study is that the DePaul and Newcastle samples did not require proof of a physician diagnosis of ME or CFS; however, all participants included in the study’s analyses fulfilled the symptom requirements of the IOM or revised London criteria.