Dear All
A literature search on the validity of visual analogue scales will yield quite a number of relevant references.
One that is perhaps directly pertinent (and supports the point made by Ted) is as follows:
Williams, A. C. C., Davies, H. T., & Chadury, Y. (2000). Simple pain rating scales hide complex idiosyncratic meanings. Pain, 85(3), 457-463.
Abstract: Assumptions of reliability and consistency of self-report of pain by patients using visual analogue scales (VAS) and numerical rating scales (NRS) are based on narrow considerations of possible sources of error. This study examined patients’ use of VASs and NRSs, by their own description, with particular attention to rating of multiple pains, of different dimensions of pain, and of interpretation and use of lower and upper endpoints and increments on the scales. These have implications for the approximation of the scales to psychometric requirements. An interview developed from a small pilot project was given to 78 volunteer chronic pain patients embarking on a pain management course, and consisted of both forced choice questions and free response. Data are described with reference to lack of concordance between patients and of consistency within patients; responses suggested that ratings incorporate multiple partially differentiated dimensions of pain, with particular importance placed on function or mobility. Labels assigned to scale endpoints by researchers, whether lexical or numerical, appeared to affect their use; however, covert relabelling of scale points was revealed in free response. The action of arriving at a rating is better conceptualised as an attempt to construct meaning, influenced by and with reference to a range of internal and external factors and private meanings, rather than as a task of matching a distance or number to a discrete internal stimulus.
Tom Sensky
Tom Sensky BSc PhD MB BS FRCPsych
Emeritus Professor of Psychological Medicine
Imperial College London
e-mail: [log in to unmask]
-----Original Message-----
From: Evidence based health (EBH) [mailto:[log in to unmask]] On Behalf Of Ted Harding
Sent: 19 July 2017 12:46
To: [log in to unmask]
Subject: Re: pain: psychological or physical
Jeremy,
I'm not at all clear why you want a "definitive" attribution (amongst your categories) of pain "measured by a visual analog scale" (VAS).
When a subject ticks a box on a VAS, that is a record of *perception* of intensity of pain. As a perception, that has to be primarily psychological (from a definitional point of view).
However, the intensity of perception could be very directly driven by the physical (including physiological) mechanisms giving rise to the pain; and they could also be modulated by psychological processes.
As an example of this: Say you knock you head on a door-frame.
Then you can (or most people can) hold that pain "at arm's length"
by a psychological effort (e.g. concentrating on something else), and then be less distressed by the pain.
By contrast, if the pain is perceived via the sympathetic nervous system (e.g. from a gallstone or a kidney stone) then it is almost imposssible to hold it "at arms length" by conscious effort.
And then, when drugs are administered, what is their primary action?
Perhaps to counteract the primary physiological process generating the pain (e,g, anti-inflammatory drugs); perhaps to inhibit the neurological transmission of pain signals; perhaps (e.g. anaesthetics) to suppress tha brain's perception of pain (and possibly everything alse as well).
Given the complexity of attributing pain to "physical" pain or to "psychological" pain. I do wonder what the point of your question is!
And I have not included the "purely phychological" pain which is what is imagined (without any physical trauma whatever) by someone whose brain is going off the rails!
Best wishes,
Ted.
On Wed, 2017-07-19 at 11:00 +0000, Jeremy Howick wrote:
> Dear List Members,
>
>
> Within the context of a trial or systematic review, is change in pain
> (for example with a visual analog scale): (a) physical outcome, (b)
> psychological outcome, or (c) both.neither?
>
>
> I am aware that many causes of pain (such as bumping my head into a
> low door frame) are purely physical. What I am interested in is
> whether pain as an outcome measured by a visual analog scale itself is
> physical, psychological, or both/neither.
>
>
> I’m specifically interested in what the scientific consensus is or,
> better, whether there is evidence of some kind that could resolve
> this.
>
>
> Thanks in advance,
>
>
> Jeremy
>
> T: +44 (0)1865 289 258 E: [log in to unmask]
>
> http://www.phc.ox.ac.uk/team/jeremy-howick
>
>
>
> Nuffield Department of Primary Care Health Sciences, University of
> Oxford Radcliffe Primary Care Building, Radcliffe Observatory Quarter,
> Woodstock Road, Oxford, OX2 6GG
>
>
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