For those of you who have done one, you will know that finishing your PhD can be a bit like sailing in front of Wild Oats in the Sydney to Hobart – the flapping spinnaker, full of midnight oil and editorial mutterings, left limp as a soggy biscuit. For those of you who have not done a PhD, you might not get it. Well, here at BiM we are keen to keep the doctoral ginger nut from dropping into the tea cup of discontent by giving new graduates the chance to tell us about their work. This one is from the aptly named Keith Smart, from University College Dublin. It is an important series of studies because it takes a proper stab at integrating modern pain science with manual therapy practice. That is, Keith and his supervisors have said something along these lines – ‘if the physiologists argue that tissue damage, peripheral neuropathic changes and central sensitisation can underpin pain, then let’s see if clinicians can tell when they do’. However, they haven’t just gone there, they have done the background studies too. I won’t do it justice, so have a quick read.
The development and preliminary validation of mechanisms-based classifications of musculoskeletal pain
‘Nociceptive pain’ (NP), ‘peripheral neuropathic pain’ (PNP) and ‘central (sensitisation) pain’ (CP) have been suggested as mechanisms-based classifications of pain. Some think that classifying pain in this way might i) help clinicians to better understand clinical presentations of pain and ii) improve outcomes by encouraging clinicians to direct treatment towards the underlying neurophysiological mechanisms responsible for the generation and/or maintenance of patients’ pain. But before their use in clinical practice can be recommended classification systems should be developed and validated using appropriate methodologies. The purpose of this research project was to develop mechanisms-based classifications of musculoskeletal pain and then evaluate their construct validity.
Studies and results
In the first study we used a Delphi survey method in order to generate lists of clinical criteria thought to reflect a dominance of NP, PNP and CP mechanisms. In the second study we investigated the reliability of clinical judgements and criteria associated with these mechanisms-based classifications of pain. And in the third study we investigated the discriminative validity of these categorisations by looking at whether or not patients with low back (± leg) pain classified in this way could be differentiated from one another on the basis of discriminatory clusters of symptoms and signs. The findings from the Delphi survey generated lists of clinical criteria associated with each category of pain, the findings from the reliability study suggested that such classifications might be performed reliably, and findings from the validity study suggested that NP, PNP and CP could be accurately predicted from a cluster of 7, 3 and 4 symptoms and signs respectively. We also found that patients classified with a dominance of CP reported more severe pain, poorer health-related quality of life, and greater levels of functional disability, depression and anxiety compared to those with PNP and NP. A similar pattern of findings was found for those with PNP compared to NP.
Implications for practice
Together these findings provide some evidence that clinicians might be able to distinguish between patients with an assumed dominance of NP, PNP and CP by identifying a small number of symptoms and signs. Also, the differences in health parameters between categories might reflect clinically meaningful differences associated with the multidimensionality of pain.
About Keith Smart
After escaping from his original home town of Bromley in the UK Keith went to University College Dublin (and bought the t-shirt) in his adopted hometown of err…. Dublin, to do his PhD thesis. He fitted in to life in Ireland well and some have noted a tendency towards Irish-sounding colloquialisms creeping in to his day to day discourse. Since finishing up earlier on this year, he has now returned to full-time clinical practice at St Vincent’s University Hospital, Dublin. Keith has attacked this research question with the same rigour and energy that he applies to his need to catch every single Manchester United European Cup match (wherever he is in the world), his love of dark chocolate digestive biscuits and his unequivocal (yet non-violent) approach to managing Kuala Lumparan pickpockets. So it was always going to be a quality job. Clearly he didn’t write this bio…
Smart KM, Blake C, Staines A, Doody C (2010). The reliability of clinical judgments and criteria associated with mechanisms-based classifications of pain in patients with low back pain disorders: a preliminary reliability study Journal of Manual and Manipulative Therapy, 18, 102-10 : 10.1179/106698110X12640740712897
Smart KM, Blake C, Staines A, & Doody C (2010). Clinical indicators of ‘nociceptive’, ‘peripheral neuropathic’ and ‘central’ mechanisms of musculoskeletal pain. A Delphi survey of expert clinicians. Manual therapy, 15 (1), 80-7 PMID: 19679504
Smart, K., O’Connell, N., & Doody, C. (2008). Towards a mechanisms-based classification of pain in musculoskeletal physiotherapy? Physical Therapy Reviews, 13 (1), 1-10 DOI: 10.1179/174328808X251984
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