Support for extended classification of pain states

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We welcome the recent review “Do we need a third mechanistic descriptor for chronic pain states?” by Kosek et al.2 and their invitation to expand this discussion to the wider pain community. We are acutely aware of the need for internationally agreed pain terminology that is consistent, widely recognised, clinically useful, and allows for iteration as more research emerges regarding our understanding about pain.
As Kosek et al.2 highlight, current approaches impose a binary classification between nociceptive pain and neuropathic pain. The authors also outline emergent issues associated with the recent redefinition of neuropathic pain by the IASP in 2011 and the associated clinical criteria for classifying neuropathic pain,5 leaving a substantial proportion of patients with pain unclassified.
As clinical and research physiotherapists working with people with musculoskeletal pain and disability, we agree that this current binary system fails to acknowledge, or apply to, a sizeable subgroup of our clinical population. In clinical practice, this has many possible adverse consequences including:
Kosek et al.2 suggested the following 3 proposals: (1) the assertion of nociceptive pain, (2) confirmation of the definition of neuropathic pain (but not as default), and (3) the need for a third mechanistic descriptor for people living with chronic pain that may serve to address some of the issues highlighted. With respect to items 1 and 2, we agree with current definitions and that pain classifications of nociceptive pain and neuropathic pain should not be dichotomous. With respect to item 3, we strongly support the arguments made for a third descriptor. It may be useful to note that some of us have previously published frameworks and models that attempt to address this issue and provide support for an expanded classification system of pain.1,3
As the topical review by Kosek et al. was positioned as a proposal welcoming debate, we would like to contribute by raising the following points:
Point 1. The intention of the third descriptor described by Kosek et al. is “… to distinguish patients suffering from conditions where altered nociception has been documented from those where the pain mechanisms are still truly unknown.” This raises the following issues:
Point 2. Information regarding what processes will be engaged to progress this proposal would be welcome. Is this an IASP taxonomy committee task, and if so, how will the wider clinical and research community be engaged (eg, the use of a Delphi process, which could also capture perspectives on relevant clinical criteria that may characterise a third descriptor)? Previous research has adopted similar approaches to identify characteristics of centrally mediated pain in musculoskeletal conditions,4 yet further work is likely needed to develop broader consensus that has clinical applicability.
We would welcome further discussion on this topic, and specifically the issues raised.
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