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Prevalence, Incidence, and Classification of Chronic Fatigue Syndrome in Olmsted County (CDC study)

Discussion in 'Latest ME/CFS Research' started by Dolphin, Nov 20, 2012.

  1. Dolphin

    Dolphin Senior Member

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    Free full text: http://www.mayoclinicproceedings.org/article/S0025-6196(12)00923-8/fulltext


    This study was part funded by the CDC CFS program and involves many of the team there.

  2. Dolphin

    Dolphin Senior Member

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    I've various observations on the full text I'll add here.

    The paper doesn't clearly indicate how different this prevalence figure to the last CDC prevalence study (Reeves et al., Georgia, 2007, 2.54%). The prevalence in this study is less than 3% of that figure.

    It talks about different estimates for the prevalence but doesn't indicate that some of these used the Oxford criteria.
    I'm not sure any Fukuda studies gave prevalences of over 1% (or perhaps there was some small sample, looking at GP attendees, which gave over 1% but that's an artificial subset). The prevalence of 2.54% from the Georgia study really stands out in terms of how big it is.
    The Georgia study claimed to used the Fukuda criteria: the empiric criteria supposedly operationalise the Fukuda criteria - but it is done in a really weird way.
    --------

    They do mention this % may be artificially low:

    However, they don't explain that this might mean that some patients would not meet the threshold for 4 out of 8 symptoms, reducing the prevalence.

    I'm not sure if they explicitly explain about the problems in general with this sort of retrospective analysis. Patients are not necessarily going to mention every symptom they have so again other CFS cases are probably being missed.

    It is the case that the ISF group in this study isn't very big either so even if all of them were added in it would only bring the prevalence up to 145 per 100,000.
    However, patients may not be explicitly mentioning fatigue - I was more focused on muscle pain when I was more mildly affected: that was the thing that was preventing me doing a lot of things I wanted to do.

    -----
    I would have found this a lot more interesting if they had given data for matched controls, or even some sort of background data. Surely the more interesting point is how these relate to the general population?

    For example, in the results section, they said the CFS group are:
    However, in the discussion they say:
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  3. Dolphin

    Dolphin Senior Member

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    Further points:
    A minor point is "Reasons for CFS Exclusion" - I'm very curious about this group
    - it would be interesting to have a bigger list of missed diagnoses there are similar to CFS, perhaps containing more interesting/unusual diagnoses.

    ---
    I find this statement strange - there are a variety of codes mentioned.

    Also, this ignores any cases that doctors missed completely (i.e. there wasn't enough information to pick up some CFS cases from the records).

    ---

    Although I'm not 100% sure what they're saying in the underlined part, it looks like they might be saying that because CFS has shared symptoms with other conditions, the aetiology/pathophysiology may be related. If so, this may be a "bad" sign in terms of the authors views given the mention of psychiatric disorders.

    ---


    It seems they may be suggesting that CFS is simply a collection of missed diagnoses rather than a thing by itself?

    This is at the very end. I don't know if it was a suggestion from a reviewer but the wording ("may be", etc.) is odd.
  4. Kati

    Kati Patient in training

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    The other variable worth mentioning is that physicians do not necessarily record all the symptom complaints from the patients. After reading my own GP office notes, I was apalled at how little she has been writing all along despite me describing my symptoms each and every time I would go in.

    Edit to add: Physicians also tend to structure their notes around the diagnosis they have in mind, sometimes leaving vague symptoms behind because it does not describe the diagnosis.
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  5. WillowJ

    WillowJ Senior Member

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    another point about anxiety and depression, is that this may represent physician bias about patients who are difficult to immediately classify and who have fatigue or pain or other symptoms (especially many symptoms), rather than actual anxiety and depression on the parts of all patients for whom that was charted.

    clearly some of us will have those things.

    in other cases it represents the doctor not knowing what is going on so they chart an equivalent of "not my problem" which is considered professionally acceptable,

    or non-pathological emotions are misperceived (I cannot get any help and I may be frustrated or discouraged about that, or I may be worried whether I will be understood or helped, is often interpreted as pathological depression and/or anxiety rather than a realistic response to life circumstances) (I being, any patient)
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  6. Dolphin

    Dolphin Senior Member

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    Yes, on a personal note, I remember before being diagnosed, crying when I was in with one of the college GP's surgery (you could get free appointments on campus so I tended to go to them than the family GP). I actually had a very stable mood on a day-to-day basis: I had read information on positive mental health and did things like doing an thing you enjoy thing every day, etc. I probably hadn't cried once anywhere in the 12 months before this (and wasn't on antidepressants or anything). Yet, crying once could get depression written on your notes (not sure if it happened in my case).
  7. Dolphin

    Dolphin Senior Member

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    Regarding this, they claim:
    I may have missed it but I don't recall any evidence the patients had thorough psychiatric evaluations. In prevalence studies, each patient with got proper psychiatric assessments with long detailed interviews. I didn't see any evidence of this. This makes me suspicious of the psychiatric rates in the CFS cases quoted. Alternatively maybe those were the patients where GPs note symptoms like fatigue, etc while lots of other non-depressed cases don't make it on the radar.
  8. Snow Leopard

    Snow Leopard Senior Member

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    They were pretty heavy handed on the exclusions, eg: Pregnancy within 12 mo before CFS diagnosis. Eg this removed 29 patients, which reduced the total number from 105 to 76. Along with Restless legs syndrome/periodic limb movement disorder (another 58!).

    Including these alone would boost the prevalence (in this study) to 0.15%

    It is noteworthy that 70% of potential patients were excluded.
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  9. Dolphin

    Dolphin Senior Member

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    What I would find interesting would be long-term data from this cohort: seeing how people did over 5/10/20 years. That's an area where there's a real lack of data in the ME/CFS field. There was no mention of such a study in the paper (they did use data from 1998-2002).
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  10. Simon

    Simon

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    I'm mystified as to the point of this Reeves legacy study: they fail to follow Fukuda diagnosis procedures so how can they measure Fukuda prevalence? Specifically, they merely trawl through medical records while Fukuda requires eg full medical & psychiatric examination, and specific lab tests. Game over.

    Even if it wasn't, if Olmsted county, like the rest of the US, doesn't have universal healthcare, then many CFS cases may be excluded simply because they can't afford access to doctors.

    I'm hoping that CDC studies in the post-Reeves era will be more altogether useful than this one.

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