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Reliability and validity of Short Form 36 Version 2 to measure health perceptions in [CFS]

Discussion in 'Latest ME/CFS Research' started by Dolphin, Aug 31, 2013.

  1. Dolphin

    Dolphin Senior Member

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    *I've given each sentence its own paragraph
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  2. Dolphin

    Dolphin Senior Member

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    ------
    Last paragraph, before the limitations section which is at the very end:


    *I've given each sentence its own paragraph

    **The cut-offs:
    1 day later:
    This meant that individuals who scored below the bolded marks on that particular SF-36 v2 subscale before doing any testing were likely not to have recovered 24 hours after the first exercise test.

    ***The cut-offs:
    7 days later:
    7-day recovery

    This meant that individuals who scored below the bolded marks on that particular SF-36 v2 subscale before doing any testing were likely not to have recovered 6 days after doing the second of two exercise tests.
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  3. Dolphin

    Dolphin Senior Member

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    The SF-36 v2 questionnaire can be seen here:
    http://www.healthmeasurement.org/pub_pdfs/_QUESTIONNAIRE_SF-36, version 2.pdf

    A lot of the questions are ask about the last four weeks, so it's probably not that surprising that in this study, with the small sample sizes there were, no group x test interactions that were statistically significant: for a lot of the scores for people with CFS, there was virtually no change. However, other sorts of tests at seven days might have found differences.
  4. Guido den Broeder

    Guido den Broeder *****

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    A rather weird study. This is by no means a validation. As you say, the questions are about the last four weeks. But no participant will have answered with that in mind.

    Nor can the conclusions be generalized. The study says nothing about the validity and reliability of the SF36 for measuring the effects of some therapy, which is how it is most often used (and where it fails hopelessly).
  5. Dolphin

    Dolphin Senior Member

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    I suppose I should say that the SF-36 v2 scores at 7 days were only a part of the study.
    They did compare the baseline SF-36 v2 scores with MFI-20 baseline scores and baseline SF-36 v2 scores with those who then went on to report symptoms.

    There isn't really a problem with "last four weeks" aspect for the baseline SF-36 v2 scores; the "four week problem" only arises when one brings in the scores at seven days, so only part of the study.
  6. biophile

    biophile Places I'd rather be.

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    "Thirty-one percent of subjects with CFS still rated themselves as incompletely recovered at 1-week follow-up." When I overdid it once in a GET program, I thought I was virtually "recovered" by the next session one week later, but then I did less and suffered more later, suggesting I was not completely recovered. There may be an extra period of vulnerability once the obvious post-exertional symptoms subside, something which I have observed many other times as well.
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  7. alex3619

    alex3619 Senior Member

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    Interesting. I wonder though if there are any studies showing how changes in attitude can alter SF-36 scores without altering real functioning? That is the confounding factor we appear to be facing.
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  8. Valentijn

    Valentijn Activity Level: 3

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    This is something I wondered about for PACE and deterioration - I think I scored 0 for one of the SF-36 scales while just mostly housebound and able to get to clinics once in a while. So how do they determine deterioration for someone that starts at 0? And if deterioration of greater than 20 points is required (was that mentioned somewhere?), that would mean that everyone at 20 and under technically could not deteriorate, even if their condition became much worse.
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  9. Dolphin

    Dolphin Senior Member

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    I imagine you scored 0 on Role Physical. A lot of people with ME score 0 on that.
    However, that wasn't used. What they sued was SF-36 physical function. It is the 10 questions at number 3 here: http://www.anapsid.org/cnd/files/sf36.pdf . I very much doubt people able to take part in the trial would have scored 0 on this: it's 5 points for each "yes, limited a little" and 10 points for each "no, not limited at all".

    However, requiring a 20 point drop at two consecutive points is quite a big drop: somebody would really have to be very ill to do that if they started at, say, 30 points.
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