Discernment of Mediator and Outcome Measurement in the PACE trial, Chalder,Goldsmith et al, 2021

Sly Saint

Sly Saint

Senior Member (Voting Rights)
preprint
Abstract
Background: When measuring latent traits, such as those used in psychology and psychiatry, it can be unclear whether the instruments used are measuring different concepts. This issue is particularly important in context of mediation analysis, since for a sound mediation hypothesis the mediator and outcome should be distinct. We sought to assess the extent of measurement overlap between mediators and outcomes in the PACE trial (n=640). Methods: Potential measurement overlap was assessed using generalised linear latent variable models where confirmatory factor models quantified the extent to which the addition of cross-loading items resulted in significant improvements in model fit. Results: Out of 26 mediator-outcome pairs considered, only six showed evidence of cross-loading items, supporting the suggestion that mediator and outcome constructs in the PACE trial were conceptually distinct. Conclusions: This study highlights the importance of assessing measurement overlap in mediation analyses with latent traits to ensure mediator and outcome instruments are distinct.

Competing Interest Statement
TC has received royalties from Sheldon Press and Constable and Robinson. Funding for the PACE trial was provided by the Medical Research Council, Department for Health for England, The Scottish Chief Scientist Office, and the Department for Work and Pensions. The authors declare no other conflicts of interest.

Funding Statement
This paper represents independent research part funded by the National Institute for Health Research (NIHR) Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust and King's College London and Applied Research Collaboration South London (NIHR ARC South London) at King's College Hospital NHS Foundation Trust. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. EC and SV are fully funded by the NIHR BRC; TC is part-funded by the NIHR BRC; KG is part-funded by the BRC and ARC.

Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study uses data that have previously been published (Chalder et al. 2015; Ryan et al. 2017). The original PACE study was approved by the West Midlands Multicentre Research Ethics Committee (MREC 02/7/89).

All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.

Yes
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https://www.medrxiv.org/content/10.1101/2021.01.25.21250436v1

https://www.medrxiv.org/content/10.1101/2021.01.25.21250436v1.full.pdf
 
This is exactly what people mean by lies, damn lies and statistics. Fiddling with GIGO data in blatantly biased ways is lying just the same. It's not even lying with a few extra steps, it's lies on top of lies, lies all the way down.

What is the overlap between the angels dancing on hairpins' shoes and adherence to the surface of the hairpins? Blue. Or something. This is not a discussion of substance, it's just made-up BS. The discussion doesn't matter and neither does the answer.
 
Please forgive my inability to remember specifics, but didn't someone, perhaps JohntheJack?, do a freedom of information request for some important PACE data but was denied it because no-one could access the data anymore... I think this is even the second paper released since then. Perhaps worth getting back to them, with this as evidence that someone clearly can still access the data... Just an idea, for something good to come out of this. Kx
 
Kirsten said:
Please forgive my inability to remember specifics, but didn't someone, perhaps JohntheJack?, do a freedom of information request for some important PACE data but was denied it because no-one could access the data anymore... I think this is even the second paper released since then. Perhaps worth getting back to them, with this as evidence that someone clearly can still access the data... Just an idea, for something good to come out of this. Kx
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I am hopeless remembering details but wasn’t this after Prof (White) had retired and his retirement was given as the reason that the data was no longer accessible, even though the eminent professor was still regularly giving lectures to insurance companies and was subsequently listed as the lead researcher in the ten year PACE follow up study.
 
Since this is about the observer and the observed -- shouldn't the observer also be part of the study and go through the same process of having their distinct mediators and outcomes assessed in order to better understand their effect on interpreting their observations?
 
I have no idea what this abstract means. All I glean from it is that a statistician who wanted a nice big data set to play with did lots of fancy stats and drew conclusions that probably are completely unrelated to reality.
 
I suspect this being psychodramaology that all of the concepts / constructs are not able to be properly scientifically validated and rely solely on the people who deem themselves qualified (and with interests now vested) on creating and validating (through observation) that these are all true.
 
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