M.A. Shraim1, H. Massé-Alarie2, P.W. Hodges1
1The University of Queensland, Brisbane, Australia, 2Université Laval, Quebec, Canada
Background: Mechanism-based classification of pain has been advocated widely to aid tailoring of interventions for individuals experiencing persistent musculoskeletal pain. Three pain mechanism categories are defined by the International Association for the Study of Pain: nociceptive, neuropathic, and nociplastic pain. Discrimination between them remains challenging because of limitations in diagnostic tests, lack of consensus regarding the possible mechanisms, characteristic features, and methods to discriminate between them.
Purpose: This study aimed to: (1) build on a framework developed to converge the diverse literature of pain mechanism categories to systematically review clinical and laboratory-based methods purported to discriminate between them; (2) synthesise and thematically analyse these methods to identify convergence and divergence of opinions; (3) report validation, psychometric properties and strengths/weaknesses of these methods; and (4) present an overall synthesis of the most commonly used methods/findings to discriminate between pain mechanism categories.
Methods: Three databases were searched to identify papers that discuss methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system. Data were extracted and thematically analysed to identify methods proposed to discriminate between mechanism categories and their associated findings. Studies that assessed the validity of methods to discriminate between categories were assessed for quality.
Results: Extraction and thematic analysis were undertaken on 184 papers. Most papers discussed discrimination between nociceptive, neuropathic, and nociplastic pain, whereas a small portion discussed discrimination between disputed categories of sympathetic and psychogenic pain. Data synthesis identified 200 methods in five themes: clinical examination, quantitative sensory testing, imaging, diagnostic and laboratory testing, and pain-type questionnaires. Multi-component classification systems featuring a combination of methods were also identified. Three specific methods (temporal summation protocol, diagnostic anaesthetic blocks, and urine analysis), many pain-type questionnaires, and some multi-level classification systems have been tested for validity for discrimination between pain mechanism categories.
Conclusion(s): There was general convergence but some disagreement regarding findings that discriminate between pain mechanism categories. A combination of features and methods, rather than a single method, was generally recommended. Some major limitations were identified: overlap of findings of methods between categories due to mixed presentations, many methods consider discrimination between two pain mechanism categories but do not consider the other mechanism, and validity of methods for discrimination between mechanisms tested by comparison with clinician/expert opinion.
Implications: The results of this review provide a foundation to undertake an expert consensus process to refine methods to discriminate between mechanisms that explain musculoskeletal pain. Identification of consensus-based methods to discriminate pain mechanisms has potential application in research and clinical practice. Most notably, it could help to disentangle the heterogeneity in pain presentations, with benefits for treatment tailoring and predicting prognosis.
Funding, acknowledgements: Study supported by NHMRC grant(APP1091302). PH upported by NHMRC Fellowship(APP1102905). HMA supported by CIHR Fellowship(358797). MS supported by post-graduate scholarship.
Keywords: pain, mechanisms, classification
Topic: Pain & pain management
Did this work require ethics approval? No
Institution: The University of Queensland
Committee: Human Research Ethics Committee
Reason: Systematic review
All authors, affiliations and abstracts have been published as submitted.
