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We are grateful to Dr Moloney et al. for acknowledging the need for a third mechanistic descriptor for chronic pain states, for sharing their own work within this field,1,2 and for raising interesting questions for debate.3 As they point out, there is a need for a consistent, international, clinically useful pain terminology that is updated as more research improves the current understanding of pain mechanisms. It is encouraging that these authors agree with our argument that the current binary classification into nociceptive and neuropathic pain leaves large patient groups without a valid pathophysiological descriptor, which has negative consequences for communication, treatment choices as well as an exaggerated focus on peripheral tissue dysfunction. It is gratifying that the authors acknowledge the need for a third descriptor, ie, nociplastic/algopathic/nocipathic pain for pain that arises from altered nociception (despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system causing the pain).2
Dr Moloney et al. raised the question whether the third mechanistic descriptor could also be applied to patients suffering from acute pain or, as we would rephrase it, the pain of or associated with acute tissue damage, in which there is no question as to whether actual nociception is occurring. There is no a priori reason why not, but the question then arises, why would it be needed in those circumstances? A different situation may occur in the case, for example, of a patient with “fibromyalgia,” whose usual pain may fit the third descriptor, but who then incurs a bone fracture. Would it necessarily follow that such a patient would experience “more” pain? Until sophisticated psychophysical studies are performed in such circumstances, the question of Moloney et al. cannot be addressed with confidence. For the time being therefore, we suggest that the use of the third descriptor be restricted to chronic pain states.
Moloney et al. pointed out that “Pain ‘descriptors’ in this classification system may not necessarily be synonymous with the reasons for, or reflect all mechanisms underlying, ongoing pain.” As in the cases of “nociceptive” and “neuropathic,” this third descriptor refers only to the somatic or biomedical dimension of pain, when conceptualized in a biopsychosocial framework. As such, these mechanistic pain descriptors are important for communication in the clinic and in research. In fact, the use of these descriptors has the potential to improve diagnostic efforts and treatment. In clinical practice, an assessment of a chronic pain patient is not complete without the definition of the type of pain (nociceptive/neuropathic/nociplastic [algopathic/nocipathic] or combinations thereof) as well as an International Classification of Diseases, Tenth Edition pain diagnosis, fibromyalgia, disk herniation, etc. The reason is that one diagnostic entity, such as lumbar disk herniation can give rise to several different pain types, typically nociceptive pain in the back and neuropathic leg pain. The dominant type of pain typically informs the choice of treatment in the “bio-” dimension of the biopsychosocial framework. However, we agree that any mechanistic classification of pain, as well as the International Classification of Diseases, Tenth Edition diagnostic classification, constitutes only one part of that broader framework that should always be applied in the assessment and treatment of patients with chronic pain.
Furthermore, Moloney et al. are concerned that a third descriptor might encourage an algorithmic approach to care. However, we are not advocating that care should focus on the mechanistic descriptor classifications alone or predominantly. By contrast, we agree with the authors that clinical care should be planned in the context of all dimensions of the clinical presentation, in collaboration with the patient.
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