But they walked, hopped and jumped on it!

From the days of my infancy as a physiotherapist, I was raised on the teaching that pain should be measured by subjective means only. You have to ask the patient. You cannot presume to judge the magnitude of their experience: you ask them, and they tell you. If they say it’s a 2 out of 10, that’s what it is. If they say it’s an 11 out of 10 (I see you smile as you recognise this experience), that’s what it is. Countless students have challenged this: “What if the patient walks, jogs and hops on the painful ankle, and then says the pain is 10/10?” But the reply was always: “Their pain is as bad as they say it is. You have no better way of measuring it.”

I think that this is standard fare in the clinical world, for many good reasons. But take a look at the psychology literature, and you’ll see experimental “pain” being measured using all sorts of other approaches. Subjective ratings are not enough: one must also measure the psychophysiological expressions of pain. Arousal is a big focus for measurement: skin conductance is used to estimate how much the participant is sweating, or the acoustic startle response – the strength of the reflexive eyeblink in response to a sudden noise – is used to estimate how alert the participant is. Avoidance behaviour can also be assessed: response latency time tells us how long the participant hesitates for before they respond to a given instruction. But can these really tell us about pain?

As a clinical physiotherapist, my automatic response is “No! Those are behavioural responses! They may be related to pain, but they don’t quantify pain itself.” And that’s all well and good until someone points out that subjective pain ratings, too, are behavioural responses. We have no way of knowing how accurately that subjective pain rating corresponds with the actual, lived experience of the pain.

In his doctoral thesis, Geert Crombez provides an accessible explanation of why the psychology literature displays so many different proxy measurements for pain. He argues that the actual, lived experience of pain cannot ever be directly measured. It is a latent construct. The only way to quantify something latent is by using proxy measurements to quantify things we think are related to the latent construct, and then infer the presence, absence or quantity of the latent construct. Crombez points out (and I paraphrase) that, in the context of wider society, humans infer the presence or absence of pain in others based on what we observe. We observe behaviour: she sat down very suddenly and grabbed her knee, pressing it hard and bending over it with her eyes closed and a grimace on her face. We observe physiological changes: beads of sweat started to form on her forehead. We observe an antecedent stimulus: she had just been walking very fast, looking over her shoulder, when she walked into that bollard and stopped suddenly. And we observe further behaviour: she said, “Ahhh, it hurts.” The verbal communication of pain is just another behaviour.

On the basis of this, Crombez suggests that, in research, pain ought to be inferred on the basis of 3 kinds of measurement:

1)     Subjective reporting

2)     Psychophysiological measures (muscle activity, sweating, etc.)

3)     Overt behaviour (she clutched her knee and grimaced)

I like this suggestion. The idea that we could use more than one measure, so that what we find in one might be backed up by what we find in the other, feels reassuring. And it makes sense to me that pain is not directly measurable. While I don’t think that pain can be inferred in the absence of subjective reporting, I can see the benefit of substantiating the subjective report with other measures within a research context. This approach also reflects how humans tend to infer the existence of pain in natural, social contexts.

But there are some problems, too. The correlation between the measures of these three aspects is not always as good as one might expect. In fact, with psychophysical measures, the relationship between a chosen measurement and the construct it is intended to measure may also be poor. Now, I am no psychologist, but it seems to me that this raises a question: are we sure that we know what we are measuring?

Knowing what we are measuring can be a problem when observing overt behaviour, too – in both clinical and research settings. When a person grimaces are they expressing pain? Or anticipation of pain? When they hesitate to do something are they scared? Reluctant? Tired and bored? Uncertain of the instruction? Distracted?

These are not new questions. Measurement of pain has been debated in many ways, and in many spheres. But this blog site brings together many people from many different backgrounds, which provides an opportunity for us to have a robust and helpful discussion about this. Whether you are a clinician or a researcher, I invite you to give this some thought and use the comments section: let’s talk about it.

What do you reckon? Which measures do you consider reasonable bases for inferring that someone is in pain or for quantifying their pain? What would you urge us to consider more carefully as we discuss this quandary?

Tory Madden

Tory MaddenTory arrived from South Africa to start her PhD at BiM.  She is a physiotherapist who worked clinically before turning her focus toward research.  She is interested in pretty much anything related to pain and neuroscience, thanks to some particularly inspirational teaching by Romy Parker during her undergraduate training at the University of Cape Town.

Tory is rapidly developing a fondness for Australia’s amazing TimTams, but is rather worried about whether she will survive the Adelaide winter. She loves sports but has been forced to take some time out due to a knee injury. She has used this extra time to try her hand at table tennis, with which she is making moderate progress, and rowing, at which she should not yet be left unsupervised…

Reference

Crombez G (1994) Pijnmodulatie door anticipatie (Pain modulation through anticipation). Doctoral dissertation. University of Leuven (Belgium).

Comments

  1. Tory Madden says

    Neil, I agree that one of the most challenging things about pain research is that human experience is far more complex than our models. That’s why I find the views of psychologists so helpful: I think they can help us to organise how we think about the complexities. Bronnie, thank you for so clearly articulating the importance of context! And Lesley, it is fascinating to get inside one’s own brain when trying to “be a patient”, isn’t it? I’m sure it helps us to be better at what we do…
    I have enjoyed this discussion – thanks, everyone, for getting involved and prompting reflection… I always hope that this kind of conversation will make us better clinicians, researchers and people.

  2. Lesley Singer says

    Hi
    I am enjoying reading the posts on this topic. i can remember when I was assessed at a pain clinic when I had waited on the waiting list for my turn. I knew my pain was intense to me comparing it to other painful experiences. I had been to several doctors and had been diagnosed with anesthesia dolorosa. i thought about my first appointment a great deal before I actually had it and thought about the questions I assumed I would be asked since I was a physiotherapist and had some idea. i thought a great deal about the question rate your pain on a scale of 0-10 and I really wanted help from this pain center as I was not coping very well although I was still working part time. I knew what I would rate my pain but I thought more about how thaT would be interpreted by the team. I really wanted their help so if I said 8/10 would they believe me or think I was a catastrophizer. If I said 6/10 would that be more believable and get me help. I knew I should say what I really felt i desperately wanted help .
    I just wanted to give this story to add a patient perspective but also a health care professional who at a different level should know to give an honest answer. There are different motivational reasons for the answer.

  3. Susan Tupper says

    This is one of my favorite topics (which I admit is a bit sad, but there you have it). Our lack of understanding of what we’re measuring when we ask about or observe pain behaviors leads to the many biases and misconceptions that exist e.g. people that show/report high pain in the absence of obvious pathology are malingerers, drug seekers or psychologically or physically inferior, while those that show/report low pain with gross pathology are stoic, tough, “good patients” or a hockey player (Canadian humor). Physiological and behavioral validations of pain reports are an interesting concept, but I think they are not a solution. This is particularly true for people with chronic pain where you see habituation of the physiological and behavioral changes over time. From an energy conservation perspective, it is not cost efficient to display pain behaviors continually despite ongoing pain. Some patients may turn on and off their behaviors depending on the audience, e.g. it’s not useful to display pain in front of a clinic receptionist who can’t treat you, but it is useful to display pain in front of the PT who can help. The same is true of numeric pain scores and there is interesting research in the pediatric pain realm to show differences in pain scores depending on the social context. Pain behaviors and pain reports are a social communication. Amanda C de C Williams wrote a fantastic paper on the evolutionary psychology of facial expression of pain in 2002 found at this link http://eprints.ucl.ac.uk/11898/1/11898.pdf. Ken Craig and others developed the Social Communications Model of Pain (for a recent update on the model see this link http://www.ncbi.nlm.nih.gov/pubmed/22103643). Thanks for the post, Tory, and for all the interesting comments everyone.

  4. John Quintner says

    Ruth, in medical usage the term “pain” qualifies as being a symptom, whereas pain behaviours do qualify as natural signs. The messages that pain behaviours convey are dependent upon a number of different dimensions and many possible components. [Vlaeyen et al. 1987] They are highly influenced by culture, by contextual factors, as well as by the beliefs and appraisals of the person in pain. The clinician may misattribute the intent of the message, or indeed not know whether a message was intentionally sent. Some behaviours can be laden with meaning for the clinician when the “sender” intended no such meaning. The point I am trying to make here is that the lived experience of pain is not captured through the observation of pain behaviours. In other words, pain is NOT simply the sum total of its associated behaviours.

    Tory, I would be interested to learn how Kerwin Talbot proposes to tease apart the sensory and anhedonic components of the pain experience.

    Reference: Vlaeyen JW et al. Dimensions and components of observed pain behaviours. Pain 1987; 31: 65-75.

    Tory Madden Reply:

    Hello John. I’m not sure how far Kerwin is with working out how to distinguish the components of pain, but I’ll pass on your question to her and copy Lorimer in, and I expect that they will respond to you directly. Thank you for your interesting thoughts!

  5. John Quintner says

    Ruth, would you please explain the type of behaviour that you think should not be reinforced by health professionals? Could you also indicate why you say that such behaviour does not serve the patient well?

    On another note, I must say that I do not agree with you when you say that the subjective report should be regarded merely as “verbal behaviour”.

    Ruth White Reply:

    Hi John
    Thanks for your comments. I accept my view is pretty skewed towards the behavioural end of the treatment continuum as I am currently working with people whose current healthcare seeking behaviours have led to a downward spiral in their well-being, most particularly around repeated opioid seeking behaviour. In this context, I suppose my train of thinking was in line with some of the early thinking of Wilbert Fordyce, that as health professionals we need to be mindful of the fact that we play an important role in patients’ learning and conditioning experiences.
    For people experiencing chronic pain and who repeatedly seek healthcare / interventions, their repeated verbal expressions of pain have in some respects become another illness related behaviour. Perhaps the person in pain does feel well served if the provider hears a verbal report of 11/10 and then provides an opioid script-but is this provider behaviour really in the patient’s best long term interests?
    I accept that we need to listen carefully and acknowledge the person’s whole experience. I do not think this is the same as agreeing with the patient’s verbal/ numerical report 11/10 etc. In fact, my preference (in the environment that I work in anyway) is not to ask about pain in this narrow way as it seems to me to reinforcing one of the behaviours we would want to extinguish!

    John Quintner Reply:

    Thanks Ruth. It was not clear to me that you were also referring to the behaviour of health professionals. Do you distinguish between health-seeking behaviour and help-seeking behaviour? Or is this just a semantic issue?

  6. Ruth White says

    Thanks Tory, such a complex and interesting topic!
    Perhaps in the clinical setting, what we have previously labelled the ‘subjective report’ could be better thought of and reported in terms of ‘verbal behaviour’. Any intervention eg expanding patient’s knowledge and perceptions would in due course likely change the verbal behaviour, and presumably any physical ‘overt behaviours’. The more experimental measures of pain seem to me to be just that, OK for experiments.
    On a final note, when discussing peoples’ chronic pain experience, I think it is a mistake/ a trap even / for health care providers to agree that “pain is whatever the patient says it is”. This simply reinforces one type of behaviour that is not serving the patient well and that is the last thing we want to do.

  7. Greg Sabo says

    I think people often report 10/10 pain (or higher) in an attempt to generate greater empathy or concern from the clinician, so that they can get the ‘really good’ treatment that they may believe we withhold for the only really serious cases. Obviously this is a false assumption made by the patient, but rather than becoming frustrated ourselves and start to think of the patient as a liar, we should look at it as a useful insight into their current psyche. . We also have to remember that pain and noxious stimuli are two different things. By definition, pain must be accompanied by an emotional response. How can we reliably and effectively quantify something as qualitative as human emotion? I completely agree that when it comes to pain, we should be looking at the 3 factors discussed in this article, but I also believe we must not stop at only these 3. There are so many components to pain, that any attempt to encompass this entire experience with a a single number or observation would be a gross underappreciation for the complexity that this subject deserves. Instead, we should continue to look for more ways to break it down and focus our research on specific aspects of the experience, rather than attempting to address the entire experience itself as one thing.

  8. Sarah Kelly says

    I think comparing pain with love is interesting. Is it a fair comparison? We tend to think of love as an emotion, and pain as a perception….. but a perception with a unique emotional quality – unpleasantness. It is interesting that we strive to measure pain. What are we trying to measure precisely? The quality of the sensation? The emotion of unpleasantness? Or the response the individual has to that pain?

    I suspect the core of the problem is, that we do not know exactly what we are trying to measure when we say we want to measure pain. This came up recently in a discussion with a group of attendees of a pain management programme. Many voiced how much they dislike the 1 to 10 scale used to ‘measure’ pain. They felt it was very unrealistic… they just didn’t get it, because it said nothing to them about their pain. One lady remarked that she would prefer to go through childbirth many times over, that experience her pain day in and day out. ‘Intensity’ of sensation (if that’s what the scale is trying to measure?) said very little about their experience of pain, and the distress it causes.

    For me, the interesting question is, why are we trying to measure pain as a quantitative ‘thing’ anyway. For research? How is it helpful? When a participant in research scores their pain from 0-10, what do *they* really mean by that? “This is how much the pain distresses me” “This is how intense the sensation is” “This is how close I am to taking action to stop it”

    It comes back to that question, do we actually know what we want to measure when we say we want to measure pain?

    Posting a link (if I can post links?)

    http://hyperboleandahalf.blogspot.co.nz/2010/02/boyfriend-doesnt-have-ebola-probably.html

    Tory Madden Reply:

    Hi Sarah

    You raise an interesting point about the various aspects of a pain experience. Kerwin Talbot, who is part of BiM, is looking into the idea of distinguishing sensory intensity and unpleasantness as part of her doctoral research. There are a few papers that I have come across (mostly in the psychology literature) that take subjective measures of these two dimensions separately. That approach may well be informed by the kind of patient interactions that you have described.
    The link you posted is very funny, but also exposes the detached nature of the measurement techniques we often use for pain. I suppose that being detached is the shortfall of much quantitative research, but, as you suggest, such detachment should not be as necessary in clinical settings. In thinking about the question you posed last, and in the context of a pain management programme, I wonder whether it would be fruitful to ask each patient which aspect of their pain matters most, and then ask them for a subjective rating of that. Of course, that might require a discussion dissecting the aspects of pain beforehand, but I suspect that most people who have had pain for some time would not find that too challenging.
    I also can’t help but think that we need more qualitative (or qualitatively-informed) research into pain…

  9. It strikes me as quite odd, reading this post. This is the model of pain and pain behaviour introduced initially by Fordyce and Loeser – and the one I learned right from the very beginning of my career in pain management.
    Triangulation of clinical assessment strategies has also been part of clinical assessment at the chronic pain management facilities where I’ve worked for many years. A combination of psychometrics, history taking, interview, physical performance measures and psychophysiological measures is not uncommon.
    Pain behaviour, including verbalisations, automatic/reflex responses, volitional behaviours and even things like going to see health professionals or lodging an insurance claim are all pain behaviours and all influenced by psychosocial factors. We simply can’t just take a person’s word as gospel truth about their pain – though it is far more useful and reliable than anyone else attempting to determine another’s pain. We need to keep in mind the various contextual factors that influence what we do when we’re sore.
    We’re never able to substantiate another person’s pain experience, that’s why we call it subjective. We can only attempt to uncover any contributory factors (biological, psychological and social), alter these and watch what happens for the individual.
    This is why I keep hammering on about the need to remember the person in the middle of the pain. Their experience, their interpretation of their experience, and the external factors that influence the expression of their experience (and our ability to interpret their expressions) are the things that must be addressed. If we don’t, we’re grasping blindly in the dark.
    And the really odd thing? We’ve known about this since the 1970’s and there are STILL people working in pain management who haven’t found out about it and think psychosocial factors are irrelevant.

  10. Great post Tory. Just a thought, why have we turned pain and love into a noun? The Greeks only had verbs for everything ie paining and loving, chairing and tabling, there were no names given to objects such as chairs or tables. Seems to make much better sense if we try to define it for a patient in these terms. Patients are able to conceptualise this and give much more personal and accurate answers.

  11. Neil Pearson says

    Sometimes when I think about pain, as a troublesome human experience a whole lot like love (or other troublesome human experiences) it helps …

    On the basis of this, Pearson suggests that, in research, love ought to be inferred on the basis of 3 kinds of measurement:

    1) Subjective reporting

    2) Psychophysiological measures (e.g., decreased heart and respiratory rates when thinking of love and when close to a loved one, pupil dilation, increased blood flow to hands and feet, decreased salivary cortisol, …)

    3) Overt behaviour (e.g., eye contact, touching frequency, …)

    Then again, lust is also a human experience. We might be more likely to find tighter correlations between one’s subjective ratings, psychophysical measures and overt behaviours there.

    I write this with no intention to mock your questions Tory. Rather, this brief discussion is to add what I reckon – the questions we ask about pain are at times related to a desire to make it into a specific measurable ‘thing’ – to fit this human experience into a research model that is much better at measuring behaviours than experiences.

  12. Neil Pearson says

    great post Tory!
    My first thoughts are that psychophysical and overt behavioural responses can be intentionally influenced, and that there are vast differences in individuals’ abilities and motivations to do so.
    The same of course goes for pain ratings, as you point out.
    (As such, I’m in some agreement with john’s reply)

    Using the measures to ‘substantiate’ pain is a path I hope we have the wisdom to avoid.
    Using the measures to understand an individual, and to add to our understanding of the complex human experience of pain, …, that makes a lot of sense.

  13. John Quintner says

    Tory, you rightly ask whether we are sure we know what we are measuring. Might I suggest that the answer could well be a resounding NO?