The 12th Invest in ME Research Conference June, 2017, Part 2
MEMum presents the second article in a series of three about the recent 12th Invest In ME International Conference (IIMEC12) in London.
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PACE Trial paper: Measurement error, time lag, unmeasured confounding etc.

Discussion in 'Latest ME/CFS Research' started by Dolphin, Aug 29, 2016.

  1. Dolphin

    Dolphin Senior Member

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    I think I will leave this to others to try to tackle

    Free full text: https://ora.ox.ac.uk/objects/uuid:e2cb5c9a-3661-4a84-be5e-816e453eea9b/datastreams/ATTACHMENT01

    https://ora.ox.ac.uk/objects/uuid:e2cb5c9a-3661-4a84-be5e-816e453eea9b

     
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  2. Esther12

    Esther12 Senior Member

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    hmmm....

    Maybe, seeing as your 'mediator' was a questionnaire about fear of activity, and your outcome was a questionnaire about physical functioning, the simultaneous change showed that it was not fear of activity that was mediating the change in partipant's SF36 Physical Functioning scores?

    As @Simon had pointed out.

    I only skimmed through without trying to take it all in (I planned to only look for interesting new results, but ended up reading more than I planned). This bit from the discussion seemed to summarise their interpretation of things:

     
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  3. trishrhymes

    trishrhymes Senior Member

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    The PACE researchers seem to have swallowed whole and undigested a pile of jargon I very much doubt Chalder and White understand.

    What they ignore is the fundamental of all statistical data analysis:

    'Rubbish in, 'rubbish out'

    In other words if you feed a sophisticated statistical model a set of rubbish data, the conclusions you draw will also be rubbish.

    Or have I missed something????
     
    Last edited: Aug 30, 2016
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  4. Sean

    Sean Senior Member

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    Another PACE paper? For a moment there I thought something important had happened.

    :p
     
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  5. BruceInOz

    BruceInOz Senior Member

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    I haven't read the whole paper and wouldn't be able to comment on the merits of the mediation analysis methods. For all I know, it may be great stuff. But if it's all being applied to subjective measures from an unblinded trial with obvious sources of bias it's
     
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  6. Valentijn

    Valentijn Senior Member

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    My guess would be that they want to do something dodgy in the future, or justify doing something dodgy in the past, and want to have a published paper on the subject which they can cite as an "authority". Then they can pretend that the claims in that paper give them permission to do dodgy things.
     
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  7. A.B.

    A.B. Senior Member

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    This is probably a response to Coyne taking aim at the mediational analysis paper. They're trying to justify themselves.
     
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  8. TiredSam

    TiredSam The wise nematode hibernates

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    Thank you for confirming my uneducated hunch.
     
  9. trishrhymes

    trishrhymes Senior Member

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    Hi TiredSam - I've just deleted that bit about my antiquated qualifications - realised as soon as I wrote it, it sounded pompous. I was just feeling so pissed off with the PACE researchers milking their nonsense for yet another load of b***sh**.

    Cheered up enormously by the Naviaux metabolomics study released today. Now that's what I call real science.
     
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  10. TiredSam

    TiredSam The wise nematode hibernates

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    Didn't sound pompous at all, I'm always heartened by how well-educated some forum members are.
     
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  11. A.B.

    A.B. Senior Member

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    You know what I think the existence of this paper means? They're afraid that Coyne will get the data of their flawed mediational analysis, and embarass them (or worse).
     
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  12. TiredSam

    TiredSam The wise nematode hibernates

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    If that's true it show how long it takes them to churn out another paper. Scholars, the lot of 'em.
     
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  13. Snow Leopard

    Snow Leopard Hibernating

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    It is surprising that they have no mention of the major limitation - that they didn't use objective measures of functioning throughout the trial. If they used such measures, then perhaps they would have been able to discover something useful. Instead we have what, the third or fourth mediation analysis study, the latest of which is just coming up with excuses as to why the previous mediation studies weren't any good.

    To the authors: We'd be more impressed if you designed and conducted the study well in the first place.
     
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  14. A.B.

    A.B. Senior Member

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    At this point I would only be impressed if they admitted that their treatment results are null and their theories untenable.
     
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  15. Bob

    Bob

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    Oh yippee! What utter, unbridled joy! Another PACE trial meditation analysis! :meh:

    They published a cross-sectional mediation analysis paper previously and had said that they planned to publish this longitudinal analysis, so we were expecting it.

    I haven't read this paper yet, but I wonder if this line from the abstract sums up their findings: "Concurrent rather than lagged mediator – outcome effects were more consistent with the data, possibly due to the wide spacing of measurements."

    It subtly suggests that they found no useful longitudinal mediation effects, but that all the changes (in outcomes and supposed mediators) were concurrent.
     
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  16. alex3619

    alex3619 Senior Member

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    Measurement error? Do they mean the whole study? ;)
     
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  17. alex3619

    alex3619 Senior Member

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    a.k.a. GIGO, or BIBO as I like to call it in relation to this kind of research, "Babble in, Babble out".
     
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  18. Bob

    Bob

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    So there was an "almost simultaneous change in mediator and outcome in these data", which means there was no evidence of a casual relationship between (supposed) mediators and the outcomes in this study. This is the same outcome as the previous mediation analysis.

    So there's nothing to see here... But they have an awfully long-winded way of going about telling us that the study demonstrated no mediation effects! (Caveat: I still haven't read the full paper, so i may be missing something.)
     
    Last edited: Aug 30, 2016
  19. Bob

    Bob

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    Just for my records...

    Goldsmith KA; Chalder TC; White PD; Sharpe M; Pickles A.
    Measurement error, time lag, unmeasured confounding: considerations for longitudinal estimation of the effect of a mediator in randomised clinical trials.
    Statistical Methods in Medical Research.
    2016
     
  20. user9876

    user9876 Senior Member

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    I don't see how you can measure measurement error without knowing ground truth. With questionnaires there will be different types of errors such as bias, serial correlation in how people answer as well as simple randomness (and then make a guess at its distribution). Flicking through the paper they just seem to include a term for it in their model.

    What is perhaps more interesting is the lack of independence in data where people answer similar questions.
     
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