Diagnosis of chronic primary pain in the context of structural deformity needs better definition

Making chronic pain count: empirical support for the ICD-11 classification of chronic pain

PURPOSE OF REVIEW

The purpose is to review the evidence that has been collected with regard to the new classification of chronic pain. In 2022, the World Health Assembly endorsed the 11 th revision of the International Classification of Diseases and Related Health Problems (ICD-11), and with it a new classification of chronic pain.

RECENT FINDINGS

The evidence from the formative field testing indicated that the categories were clearly delineated and the coverage of chronic pain excellent (<3% in remainder categories). Official WHO field tests showed that the classification works well within the technical parameters WHO classifications must conform to and outperformed the ICD-10 diagnoses in all respects. International field tests, in which clinicians diagnosed consecutive patients in settings of medium and high resources, showed substantial interrater reliability (κ = 0.596 to κ = 0.783) for the diagnoses and the clinicians rated their clinical utility as very high. Studies using complete hospital records demonstrated that with the information they contain, retrospective coding of the new diagnoses is possible and provides much more meaningful information than the ICD-10 diagnoses.

SUMMARY

The evidence supports the use of the new classification and highlights its informational gains - using it will contribute to making chronic pain count in many contexts.

The autoimmune aetiology of unexplained chronic pain

Chronic pain is the leading cause of life years lived with disability worldwide. The aetiology of most chronic pain conditions has remained poorly understood and there is a dearth of effective therapies. The WHO ICD-11 has categorised unexplained chronic pain states as 'chronic primary pains' (CPP), which are further defined by their association with significant distress and/or dysfunction. The new mechanistic term, 'nociplasticic pain' has been developed to illustrate their presumed generation by a structurally intact, but abnormally functioning nociceptive system. Recently, researchers have unravelled the surprising, ubiquitous presence of pain-sensitising autoantibodies in four investigated CPP indicating autoimmune causation. In persistent complex regional pain syndrome, fibromyalgia syndrome, chronic post-traumatic limb pain, and non-inflammatory joint pain associated with rheumatoid arthritis, passive transfer experiments have shown that either IgG or IgM antibodies from patient-donors cause symptoms upon injection to rodents that closely resemble those of the clinical disorders. Targets of antibody-binding and downstream effects vary between conditions, and more research is needed to elucidate the molecular and cellular details. The central nervous system appears largely unaffected by antibody binding, suggesting that the clinically evident CNS symptoms associated with CPP might arise downstream of peripheral processes. In this narrative review pertinent findings are described, and it is suggested that additional symptom-based disorders might be examined for the contribution of antibody-mediated autoimmune mechanisms.

Chronic pain in the 11th revision of the International Classification of Diseases: users' questions answered

ABSTRACT

The upcoming 11th revision of the International Classification of Diseases (ICD-11) will include a comprehensive classification of chronic pain for the first time, which is based on the biopsychosocial definition of chronic pain. This presents a great opportunity for pain research and clinical practice. The new classification consists of seven main diagnostic categories of chronic pain, which are further divided into increasingly specific levels of diagnoses. Each diagnosis is characterized by clearly defined operationalized criteria. Future users will need to familiarize themselves with the new system and its application. The aim of the present publication is to provide users of the ICD-11 chronic pain classification with answers to frequently asked questions regarding the ICD-11 as a whole, the ICD-11 chronic pain classification, and its application to common pain syndromes. The questions compiled here reached the International Association for the Study of Pain Task Force via different routes (e.g., at conferences, by letter, or during field testing). Furthermore, the authors collected questions posted to the ICD-11 browser and contacted early users of the classification to enquire about their most frequent difficulties when applying the new diagnoses. The authors of the present publication prepared answers to these frequently asked questions. This publication intends to act as a guide for the future users of the new ICD-11 chronic pain classification, hence facilitating its implementation.