measurement

Why do people with pain report differently on questionnaires than they do in physical performance testing?


One of the topics thrown around by people who don’t have an up-to-date understanding of pain is why people say one thing on a questionnaire, for example, what they can and can’t do, and perform quite differently when asked to do the same task in a clinic. It’s a good question, on the face of it: after all, people should know what they can and can’t do, and be consistent. If there is a difference, well obviously the physical performance test is far more objective than self-report – the therapist is right there watching, so there’s no room for doubt about which measure is The Most Accurate.

The main reason, according to these clinicians, for someone doing differently in the clinic compared with self-reporting, has to be because they’re biased. The person wants to misrepresent what they can and can’t do. Of course.

Superficially, and if you’re not knowledgeable about pain, behaviour, context and human interaction, you could be forgiven for accepting the idea that what you see in clinic is consistent with what’s being done in every day life. The physical movements are pretty much the same and the person is just being asked to do something they do all the time.

BUT – and it’s an enormous exception – humans are not robots. Not body bits that move when they’re pulled like a puppet on a string. People are meaning making, interpreting, social creatures with rapidly responding body systems that represent contexts in relation to memories, predictions and current demands.

I wrote a talk recently on some research that made my heart sing a bit. As an occupational therapist, my profession has long recognised that doing activities (occupations) that hold meaning is quite a different thing from doing a-contextual, meaningless movements. This is why occupational therapists are known to ask about what matters to you, and to use meaningful activities/occupations both as therapy and as outcome (Hitch & Pepin, 2021). The research I referred to was a proposal for an “ecologically grounded functional practice” within rehabilitation (Vaz, Silva, Mancini, Carello & Kinsella-Shaw, 2017). In this paper, the authors point out that “improvements at one level of functioning might not transfer immediately to other levels” and by this they mean that elbow flexion/extension improvements may not transfer into a person being able to feed themselves. They also pointed out that when people perform well-rehearsed activities in the context of goal pursuit – such as getting dressed, ready for work; catching a ball as part of a fast-moving game of netball; hammering a nail – the movements are not just about motor control, they’re about goal-directed behaviour in a context with an interaction between the person, the environment, any tools, the purpose of the activity and so on.

For example, if I want to eat soup, I not only need to have sufficient elbow flexion/extension, I also need to know where the soup bowl is (tried eating soup while lying down?), the texture of the soup (is it thick, thin, lumpy?), the heat of the soup (hot, cold, spicy) and even the social context – I might be OK slurping when I’m on my own, but I’m less inclined to slurp when in polite company. The way in which I carry out the flexion/extension will be very different with each contextual variation.

OK. So context matters, and both the what and why of movement will influence how I go about my performance.
What else?

Well, with a painful condition and especially when I’m not confident I can do it without increasing my pain, I’m much more likely to attempt a difficult movement task in the presence of someone who can monitor what I’m doing. Firstly that person might stop me if they think I’m doing something harmful (professional liability insurance offers some protection!). Secondly, it’s a lot harder to say “no” to someone who is right there in the room! This is called “demand characteristics” and has been associated with problems of the rubber hand illusion (Lush, Vazier & Holcombe, 2020). If someone expects you to do something, you’ll probably do it – because we social creatures don’t like to offend, because the person may inadvertently signal the response they want (see link).

There are other reasons people don’t report the same level of disability on a questionnaire and in physical performance testing: they don’t measure the same things, people forget (especially if they haven’t tried in a while), the day of physical performance testing could be a bad day (or a good day), in physical performance testing the person is usually asked to do it maybe once or twice – in daily life that same activity might be carried out many times across a day, week, month. The environment in a clinical testing environment is typically well-lit, the space around the person is clear, the noise level is usually reasonably low, the floor surface is flat and usually hard lino and free of rugs or pets, there’s minimal distraction, the only thing the person has to think of is this one movement – they’re not picking up the washing off the floor while rushing to put it in the washing machine before dashing out the door to pick the kids up from school.

Even the questions are different – “does pain interfere with…?” is a different question from “can you step up onto this step using a hand rail?”

And don’t let me even start on the meaning of performance either way – for example, if the person is really keen on getting knee surgery, might “good” performance mean they, without even knowing it, alter how they do a movement? What if the person is apprehensive about how the results of this testing might affect their rehabilitation and return to work – again without even knowing it, might this not have some influence on how the person performs?

Testing and measurement is a core skill and research area in psychology. Dang, King & Inzlicht (2020) offer some really good insights into the reasons responses differ between self-report and performance, and to be fair, they don’t even consider the influence of pain and physical capability as I have above. Pain-related performance is a specialty area of its own, nonetheless we can still draw from their paper because many of the problems they recount are absolutely part of pain and disability self-report and physical performance.

They describe the reliability paradox (that reliability = variance between individuals divided by variance between individuals + error variance) – in other words, we need low levels of between-person variability so that any experimental manipulation is maximised. But in real life, we almost always exhibit variability in our performance – so the reliability of two measures limits the correlations that can be observed between then, with lower reliability leading to weaker observed correlations.

The authors also describe the very different response processes involved in self report and performance – as I mentioned above, self-report measures ask people to reflect on what they do in real life in many different contexts that are unstructured. Performance measures take a snapshot based on performance in specific and highly structured situations. Self-report measures capture a person’s perception of their capabilities whereas physical performance reflects the observations of someone else. And performance assessments generally tap into peak performance, not daily performance – tapping into some of the discrepancies we see between “can do” and “will do” (competence-performance discrepancy).

So, when you read arguments on social media from well-known physiotherapists suggesting that the person who reports a difference between what they perceive they can do, and what they have done in a physical performance test is “biased”: know that we have absolutely NO WAY to determine “bias”, “malingering”, “faking bad”, “faking good” – and that there are many well-understood reasons for the difference in performance. Read this paper for more on why we can’t detect “malingering” in people with pain: Tuck, N. L., Johnson, M. H., & Bean, D. J. (2019, Feb). You’d Better Believe It: The Conceptual and Practical Challenges of Assessing Malingering in Patients With Chronic Pain. J Pain, 20(2), 133-145. https://doi.org/10.1016/j.jpain.2018.07.002

Dang, J., King, K. M., & Inzlicht, M. (2020). Why are self-report and behavioral measures weakly correlated?. Trends in cognitive sciences, 24(4), 267-269.

Hitch, D & Pepin, G. (2021) Doing, being, becoming and belonging at the heart of occupational therapy: An analysis of theoretical ways of knowing, Scandinavian Journal of Occupational Therapy, 28:1, 13-25, DOI: 10.1080/11038128.2020.1726454

Lush, P., Vazire, S., & Holcombe, A. (2020). Demand characteristics confound the rubber hand illusion. Collabra: Psychology, 6(1).

https://methods.sagepub.com/reference/the-sage-encyclopedia-of-communication-research-methods/i4252.xml

Numbers on a scale: How bad did you say your pain was?


ResearchBlogging.org
Have you ever been asked to give your pain rating on a scale of 0 – 10 (where 0 = no pain at all and 10 = most extreme pain you can imagine)? Have you ever tried to work out whether today’s pain is worse than yesterdays? What does a pain rating tell us?

I’ve struggled to work out how “bad” my pain is many times, is it the pain intensity that makes it troublesome? Or, in the case of a migraine, is it the quality of the pain that makes it bad (or the nausea?). Health professionals often ask people to summarise their pain experience into a form that (hopefully) we can all understand – but just what does a pain that’s around 4/10 on a VAS actually mean?

Why do we use rating scales?

We know that pain is subjective, just like taste and colour. While we might be able to agree that both of us are tasting something we call “banana”, we don’t know whether the banana taste I experience is the same as the banana taste you experience. We can see that both of us are eating the same fruit, but we don’t know how our body/brain processes that experience. Instead we assume, or infer, that we’re experiencing it in a similar way because of the similarities in context.

With pain, the situation is even more complex: we can’t determine whether the pain I feel is similar to the pain another person feels, and we don’t even have the benefit of similar “tissue damage” in the case of a migraine headache.

So, we have to infer something about the experience through some sort of common mechanism. Mostly that’s language. We hope that someone can understand that a higher number means greater pain. We hope the person can recognise what “no pain” feels like and where it might be represented on a scale. We ask the person to remember their current pain intensity, translate it into a number that in turn represents to us some kind of common understanding of what pain given that number might feel like.

Of course, there are problems with numbers on a scale. For a child who doesn’t understand the association between numbers on a scale and intensity, we use the “Faces” scale. For a person with cognitive problems (brain injury, stroke, dementia), we observe their behaviour (and hope we can translate well enough). For a person who doesn’t speak the same language as us, we might try a sliding scale with green at the bottom and red at the top, to represent increasing intensity – appealing, perhaps, to a common understanding that green = OK and red = not OK.

Worse than the difficulty translating from experience to a number is the common misunderstanding that pain severity alone represents the “what it is like” to experience pain. We know personally that it doesn’t – after all, who has had a toothache that represents “Oh no, I need a root canal and that’s going to cost a bomb!”, or “Ouch! That lemon juice in the paper cut on my finger is really annoying”, or “I feel so sick, this migraine is horrible”.

Hopefully most health professionals are taught that to use just one measure of pain is not enough. It’s important to also include other aspects of pain such as quality, how it affects function (interference), how confident we are to deal with life despite the pain (self efficacy).

So we use rating scales as a shorthand way to get to understand a tiny bit of what it is like to have pain. But the Visual Analogue Scale (VAS) is used many times to estimate whether “this person’s pain is so bad they need medication”, or “this person’s pain means we can’t expect her to help move herself from the ambulance trolley to the wheelchair”. The VAS can be used in many ways it shouldn’t be.

Studying the relationship between VAS pain intensity and disability (SF36)

The study by Boonstra, Schiphorst Preuper, Balk & Stewart (in press) aimed to identify cut-off points on the VAS to establish “mild”, “moderate” and “severe” using three different statistical approaches.  They measured pain using a Verbal Rating Scale (mild, moderate and severe), the VAS, and used several scales from the SF36 (a measure of general health quality) to establish interference from pain.

What they found was that while “mild” pain was fairly equally determined (less than or equal to 3.5), and correlated with both severity and function, when it came to “moderate” and “severe” pain, there was far less agreement. In fact, this group found that individuals could verbally rate their pain as “moderate” but at the same time report severe levels of interference. This means verbal descriptors under-represent the impact of pain on performance.

They also found that the cut-off point between “mild” and “moderate” pain in terms of interference with activity ranged between 2.5 – 4.5, and for moderate to severe pain between 4.5 – 7.4.  The associations between pain intensity and disability or interference were low to moderate and as a result these authors argue that it is “questionable” to translate VAS scores into verbal descriptors, because the different instruments measure different things.

What does this tell us?

It should be easy by now to tell that although we use numbers as a shorthand for “how bad is your pain?” in reality, they don’t directly translate the “what it is like” to have pain. Neither does the VAS correlate well with measures of disability or interference from pain. While people with mild pain might be also experiencing only a little disability, when the numbers go up the relationship between intensity and function disappear.

I think we might be trying to quantify an experience as a quick way to make clinical decisions. Really, when we ask “how bad is your pain”, depending on the context, we may be asking “do you need pain relief?”, “do you need help to move?”, “did my treatment help?” or any myriad other questions. The trouble is in research, we can’t do statistics nearly as easily on a “yes” or “really bad” or “it didn’t change much” answer. But how many of us work routinely in research settings?

I wonder whether it’s worth asking ourselves: do I need to ask for a pain rating, or should I ask a more useful question? And take the time to listen to the answer.

 

Anne M. Boonstra, Henrica R. Schiphorst Preuper, Gerlof A. Balk, & Roy E.Stewart (2014). Cut-off points for mild, moderate and severe pain on the VAS for pain for patients with chronic musculoskeletal pain Pain DOI: http://dx..org/10.1016/j.pain.2014.09.014

Questionnaire Validation: A Brief Guide for Readers of the Research Literature


Questionnaire Validation: A Brief Guide for Readers of the Research Literature. Mark Jensen.

I thought I’d give you a quick overview of a brief but very useful (and readable) article that explains how readers of research literature in pain can evaluate the literature.  It provides a summary of the issues surrounding the evaluation of pain measures by reviewing the essential concepts of validity and reliability, and how these are usually evaluated in pain assessment research.

It also has a glossary of terms used in evaluating psychometric properties of pain measures that is very helpful as a brief dictionary, and it covers just what needs to be included in any paper about a new pain assessment:

(1) the rationale for the measure (what will this measure do that previous measures cannot?);

(2) validity data that specifically addresses the uses for which the measure is being proposed; and

(3) initial reliability data.

Any psychology student (and many other health science students) will very quickly realise that there are thousands of pain measures already available, yet each year there are many more that are published.  Why oh why would we need any more?  The answer is not just that each researcher keenly wants to be ‘known’ for his or her new questionnaire – but that ‘our understanding of pain, and the effects of pain treatments, is so dependent on our ability to measure pain, any improvement in pain assessment should ultimately result in an improvement in our understanding and treatment of pain.’

Jensen writes that there are two main reasons for developing a new pain measure:

(1) that the new measure assesses a dimension or component of pain not assessed by existing measures, and

(2) that the new measure shows clear improvements over existing measures of the same pain dimension (eg, it is shorter, it is easier to administer and score, it is a better predictor of important outcomes, it is more sensitive to change).

Although this is not a new article – it was published in 2003, it summarises all the relevant psychometric areas in such a succinct and reader-friendly way that I think it should be compulsory reading for anyone learning about pain assessment (and certainly anyone in the midst of dreaming up a new measure!).

Jensen, M. (2003). Questionnaire Validation: A Brief Guide for Readers of the Research Literature. The Clinical Journal of Pain, 19:345–352.

Colour therapy…


ResearchBlogging.org
With only a small proportion of the people experiencing acute low back pain becoming chronically disabled by their pain, a holy grail of sorts has been to quickly and effectively identify those who need additional help and those who don’t.

The ‘Psychosocial Yellow Flags’ initially developed in New Zealand by Kendall, Linton & Main (1999) provides a useful mnemonic for the factors that have been established as predicting longterm disability – but requires clinicians to be aware of the flags, and record them. Because the ‘Yellow Flags’ are not ‘objective’ and can’t be summed or scored, there is no way to determine a cut-off point to identify those people only just at risk – and the tendency is to under-estimate those who need more assistance, while many clinicians report that they don’t feel comfortable or confident to assess ‘Yellow Flags’ in a primary health setting.

For those who can’t remember, the risk factors known to be associated with ongoing disability in people with acute low back pain are:

A: Attitudes and beliefs – e.g. catastrophising, a passive approach to rehabilitation, ‘Doctor fix me’, hurt = harm

B: Behaviours – e.g. resting for extended periods, poor sleep, using aids and appliances such as crutches or braces, inappropriate use of medication, self medication

C: Compensation – e.g. difficulty obtaining cover, inadequate or ineffective case management, multiple claims in the past, poor knowledge of what is available for assistance

D: Diagnosis/Doctor or treatment provider effects – unexplained technical language that is misunderstood, multiple diagnoses, multiple investigations, multiple ineffective treatments, assuring a ‘techno-fix’ is available, recommending changing jobs or stopping jobs

E: Emotions – anger, depression, sense of helplessness or feeling out of control, numbed emotions

F: Family and friends – unintentionally reinforcing pain behaviour, unsupportive of returning to work, punishing responses, or being socially isolated

W: Work – an employer who is unsupportive, history of frequent job changes or limited employment history, heavy manual work, monotonous work, high responsibility with limited control, shiftwork, working alone or while isolated, disliking the job

As I mentioned, these factors are well-known, and relatively easily recognised. Many people say to me that they have an intuitive ‘feel’ for those who will have trouble recovering from ALBP – but feel that if they ask about these factors, they risk ”opening Pandora’s box’, or being unable to extricate themselves from a complex or emotionally charged situation. Many people don’t feel adequately skilled in managing the issues involved, and would prefer to either let well enough alone, or quickly refer to someone else (Crawford, Ryan & Shipton, 2007).

Well, I don’t agree with any of those options. Although sometimes people will have ‘saved up’ a lot of their concerns and want to offload with a lot of emotion, for many people it’s a simple case of exploring what their concerns are and problem-solving around the practical issues. A referral to a psychologist or counsellor isn’t always necessary, and can for some people escalate their distress and disability.

What skills can you use to identify and manage ‘Yellow Flags’?

Open-ended questions like ‘How do you feel about your recovery so far?’, ‘Are there any things that concern you about your recovery?’, ‘What do you think is going on in your back?’, ‘What do you think this [diagnosis] means for you?’

Reflective listening demonstrates two things: (1) that you are listening and (2) that you want to understand. It should be used whenever someone begins to display emotional responses. Reflective listening can be simple ‘So from what you’ve said, I think you mean….’, or more complex ‘It seems that you think your boss wants you to go back to full duties and you’re not sure you can. I wonder if you’re feeling really anxious?’ When in doubt, reflect!

Action and responsibility – Then it can be really useful to pose this question: ‘So where does this leave you?’ or ‘What do you think you need to have happen next?’

For many people the step of demonstrating your acceptance of their point of view and understanding their distress is a good start. And many ‘Yellow Flags’ can be simply influenced by the person themselves – just being given permission to think of a solution that they’re ready to do, or being asked whether they want to hear of other options allows the person to feel more in control.

And for slightly more complex situations – such as financial strain from time off work, or difficulty within a relationship because of changed roles – these can be helped by budgetting advice, bringing the partner in to the clinic to be a part of the rehabilitation, or asking the person to think of community-based self-help organisations. Intense psychological therapy isn’t always necessary, and if misguided or not consistent with other messages about engaging in activity despite pain, can impede recovery.

And if you’re REALLY pressed for time, but still want to ‘pick winners and losers’ – a study by Westman, Linton, Ohrvik, Wahle´& Leppert (2007) finds support for the use of the ‘Orebro Musculoskeletal Pain Screening Questionnaire’, which is a 25 item questionnaire covering five groups (function, pain, psychological factors, fear avoidance, and miscellaneous which includes things like sick leave, age, gender, nationality, monotonous or heavy work and job satisfaction. It’s been used extensively in New Zealand in a compensation setting since 1999, as a screening tool to identify those who may be at increased risk of ongoing disability. This study reviews its use in sub-acute pain, with a three-year follow-up to identify the predictive validity of the instrument for sick leave.

The results are very strong – psychosocial factors as measured by OMPSQ were related to work disability and perceived health even 3 years after treatment in primary care. The screening questionnaire had discriminative power even for patients with non-acute or recurrent pain problems. The OMPSQ had better predictive power than any of the questionnaires included in the study, which included the Job Strain, the Coping Strategies Questionnaire (CSQ),
the Pain Catastrophizing Scale (PCS) and the Tampa Scale for Kinesiophobia (TSK). This study shows that among the factors, pain and function are the factors most strongly related to sick leave 3 years later.

Interestingly for me, the study demonstrated that function with focus on daily living, sleep capacity and pain experience had the most powerful predictive value concerning sick leave at 3 years. While earlier studies have shown that emotional and cognitive variables such as distress and fear avoidance beliefs have been strong predictors for 6–12-month outcomes, the best predictor in this study is having problems functioning.

The authors suggest that this probably reflects the length of the follow-up and suggests that different variables may be predictive at various stages in the process of chronification. Even though it is recognized that psychological variables are
influential factors, little is known about how and when these variables interact in the process toward disability.
Furthermore, psychological variables might operate differently for different people and at different time points.

So, this particular instrument, which has been widely used at least within New Zealand for many years, is readily available and gives clinicians and others very useful guidance on who might benefit the most from high intensity therapeutic input early.

WESTMAN, A. (2007). Do psychosocial factors predict disability and health at a 3-year follow-up for patients with non-acute musculoskeletal pain A validation of the Orebro Musculoskeletal Pain Screening Questionnaire. European Journal of Pain DOI: 10.1016/j.ejpain.2007.10.007

Crawford C, Ryan K, Shipton E (2007) Exploring general practitioner identification and management of psychosocial Yellow Flags in acute low back pain, New Zealand medical journal, 120:1254, pp U2536

           

Function


There are some very weird and crazy measures out there in pain assessment land… some of them take a little stretch of the imagination to work out how they were selected and what they’re meant to mean in the real world.

Functional measures are especially challenging – given that they are about what a person will do on a given day in a given setting, they are inherently prone to performance variation (test-retest reliability) and can’t really be held up as gold standards in terms of objectivity. Nevertheless, most pain management programmes are asked to provide measures of performance, and over the years I’ve seen quite a few different ones. For example, the ‘how long can you stand on one leg’ timed measure…the ‘sock test’ measure…the ‘pick up a crate from the floor and put it on a table’ measure…the ‘timed 50 m walk test’…the ‘step up test’… – and I could go on.

Some of these tests have normative data against age and gender, some even have standardised instructions (and some of these instructions are even followed!), and some even have predictive validity – but all measures beg the question – ‘why?’

I’m not being deliberately contentious here, not really… I think we as clinicians should always ask ‘why’ of ourselves and what we do, and reflect on what we do in light of new evidence over time. At the same time I know that each of us will come up with slightly different answers to the question ‘why’ depending on our professional background, experience, the purpose of the measure, and even our knowledge of scientific methodology. So, given that I’m in a thinking sort of mood, I thought I’d spend a moment or two noting down some of the thoughts I have about measures of function in a pain management setting.

  1. The first thing I’d note is that functional performance is at least in part, a measure of pain behaviour. That is, it’s about what a person is prepared to do, upon request, in a specific setting, at a certain time of day, for a certain purpose. And each person who is asked to carry out a functional task will bring a slightly different context to the functional performance task. For example, one person may want to demonstrate that their pain is ‘really bad’, another may want to ‘fake good’ because their job is on the line, another may be fearful of increased pain or harm and self-limit, while another may be keen to show ‘this new therapist just what it’s like for me with pain’. As a result, there will be variations in performance depending on the instructions given, the beliefs of the person about their pain – and about the way the assessment results will be used, and even on the gender, age and other characteristics of the therapist conducting the testing. And this is normal, and extremely difficult to control.
  2. The second is that the purpose of the functional performance testing must be clear to the therapist and the participant. Let’s look at the purpose of the test for the therapist – is it to act as a baseline before any intervention is undertaken? is it to be used diagnostically? (ie to help assess the performance style or approach to activity that the client has) is it to establish whether the participant meets certain performance criteria? (eg able to sustain manual handling safely in order to carry out a work task) is it to help the participant learn something about him or herself? (eg that this movement is safe, that this is the baseline and they are expected to improve over time etc).  And for the participant? Is this test to demonstrate that they are ‘faking’? (or do they think that’s what it’s about?) Is it to help them test out for themselves whether they are safe? Is it a baseline measure, something to improve on?  Is it something they’ve done before and know how to do, or is it something they’ve not done since before they hurt themselves? You see, I can go on!!
  3. Then the functional measures must be relevant to the purpose of the testing. It’s no use measuring ‘timed get up and go’, for example, if the purpose of the assessment is to determine whether this person with back pain can manage his or her job as a dock worker. Likewise, if it’s to help the person learn about his or her ability to approach a feared task, then it’s not helpful to have a standardised set of measures (unless this is a set that is taken pre-treatment and again at post-treatment). This means the selection of the measures should at least include consideration of predictive validity for the purpose of the test. For example, while a ‘timed get up and go’ may be predictive of falls risk in an elderly population, it may be an inappropriate measure in a young person who is being assessed for hand pain. It’s probably more useful to have a slightly inaccurate measure that measures something relevant than a highly accurate measure that measures something irrelevant. For example, we may know the normative data for (plucking something out of the air here…) ‘standing on one leg’, but unless this predicts something useful in the ‘real world’, then it may be a waste of time.
  4. Once we’ve determined a useful, hopefully predictive measure, then it’s critical that the assessment process is carried out in a standard way. That means the whole process, not just the task itself. What do I mean? Well, because there are multiple influences on performance, such as time of day, presence or absence of other people, and even the way the test is measured (eg If it’s timed with a stop-watch, when is the button pushed to start? When is it pushed to stop? Is this documented so everyone carries it out exactly the same way?) There is a phenomenon known as assessment drift (well, that’s what I call it!) where the person carrying out the assessment drifts from the original measurement criteria over time. This happens for all of us as we get more experienced, and as we forget the original instructions. Essentially we are a bit like a set of scales – we need to be calibrated just as much as any other piece of equipment. So the entire assessment needs to be documented right down to the words used, and the exact criteria used for each judgement.
  5. And finally, probably for me a plea from the heart – that the measures are recorded, analysed, repeated appropriately, and returned to the participant, along with the interpretation of the findings. This means the person being assessed gains from the process, not just the clinician, or the funder or requester of the assessment.

So over the Easter break (have a good one!), take a moment or two to think about the validity and reliability of the functional assessments you take. Know the confounds that may influence the individuals’ performance and try to take this into account when interpreting the findings. Consider why you are using these specific measures, and when you were last ‘calibrated’. Make a resolution: ask yourself ‘what will this measure mean in the real world?’ And if, as I suspect most of us know, your assessments don’t reflect the reality of carrying the groceries in from the boot of the car, or pushing a supermarket trolley around a busy supermarket, or squeezing the pegs above the head to hang out the washing – well, there might be a research project in it!!

Chronic Pain Assessment and Measurement


Ask anyone who has worked in chronic pain management for a while about assessment tools or measurement and you’ll see the eyes roll – how many assessment questionnaires do we need???

Firstly I want to clarify what I mean by assessment, and the difference between that and measurement.

Measurement is all about quantifying something – how much, how often, is there more of [x] than [y]? did [a] have an effect on [b]?

The problem in pain is that because pain is an individual, subjective, personal experience we can’t directly measure it. We have to extrapolate from something observable to something that can’t be seen. This means we are really measuring correlates of the pain experience rather than pain itself.

Pain assessment, on the other hand, is about learning more about the qualitative experience of pain.

In pain assessment, I am forming a ’rounded’ picture of the individual and the factors that may be associated with the experience, and hoping to answer the question I have of ‘why did this person present to me in this way on this occasion?’ I collect information over a range of domains including biophysical, psychological and social – and rely on other members of the team to help complete the picture through their assessments (I focus on psychosocial and functional).

What difference does it make?

  • Pain measurement is really helpful when trying to quantify improvement, difficulties, or to establish whether this person is more or less severely affected by their pain. Measurement is important when trying to determine whether an intervention has achieved anything (eg outcome measurement), or whether to provide a person with a certain type of treatment (eg will this person respond to anti-depressant medication?). Measurement on its own, however, won’t make any difference to your rapport, empathy or quality of your intervention. It won’t necessarily help you to understand where this person is coming from nor to prioritise your interventions.
  • Pain assessment should directly help you establish the beginning of a case formulation, or working hypotheses, about the factors that may be influencing this person’s presentation – and in doing so, should help you develop some understanding of how the problems have arisen, how they are affecting the individual, how they are being maintained, and what intervention priorities you may have.

What tools can you use for pain measurement and assessment?

Hmmmm! well there are literally 100’s of pen and paper and other measurement instruments in pain…where to start? Before I answer this, there are quite a few questions to ask yourself…

  • If you’re assessing an individual, you may not want to use any formal measurement tools – quite simply psychometric tests can’t provide you with anything more than what your patient/client is prepared to tell you. They are not X-rays of the mind! They simply organise information, may be a little more efficient at times than interview, and they should (if well-developed) be reliable (measure the same thing the same way each time they’re used), be valid (measure what they say they’re going to measure), and help you compare this person with other people who have taken the same questionnaire (provided the original group with whom you are comparing this person is somewhat similar to your client/person!).

In choosing questionnaires or measurement instruments, it’s important to ask yourself – what do I really want to find out? Why might I use a pen and paper tool when I could ask the question? What is the burden on the patient/client to fill out this questionnaire? Can I interpret it? What does it mean if I do interpret it? What does a certain score actually mean? Can it predict anything? I can use it as an outcome measure? How do I report the findings?

    Behavioural measures are not nearly as readily available, nor used, as pen and paper questionnaires. This is partly because they are time-consuming to do properly, and often involve recording the person using video or photographs, then reviewing and scoring. Training to complete behavioural measures accurately is essential to ensure inter-rater reliability (like calibrating any other measurement instrument!). The predictive validity of behavioural measures such as Functional Capacity Evaluations or Assessments has not been well-established, and it’s important to recognise that these measures are only an indication of what this person is prepared to do on this day, not ‘lie detectors’! There is no way to determine whether someone is ‘malingering’ or ‘faking’ or ‘symptom magnifying’ – and health providers should not allow themselves to try to make this type of determination, it probably belongs with investigators rather than in health.

    A great reference for assessments that may be used in pain, and including a wealth of information on concepts such as validity, reliability and so on is the Handbook of Pain Assessment (2nd Ed, 2001) Edited by DC Turk and R Melzack, published by The Guilford Press.
    This mighty tome contains 100’s of full versions of many of the assessment tools that have been used in pain and pain management. More importantly is the reference to the original articles for these tools. To be really ethical about using psychometric assessments and measures, it’s vital to read the original research, and subsequent published literature about the properties and normative data associated with the measure.

    I’ll write more about assessment and case formulation soon – keep coming back for more, or if you don’t want to miss, you can subscribe using the RSS feed above. If there is a specific assessment or measurement tool you’d like to learn more about, put it in the comments and I’ll do my best!