Abstract and Introduction
For the first time, the upcoming International Classification of Diseases and Related Health Problems, Eleventh Revision (ICD-11) will include a comprehensive classification of chronic pain, 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 7 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 in this study reached the International Association for the Study of Pain Task Force through different routes (eg, 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.
To overcome the inadequate classification of chronic pain in the International Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10), a Task Force (TF) of the International Association for the Study of Pain (IASP) developed a new and comprehensive classification of chronic pain for the upcoming ICD-11.[60,61] The ICD-11 and the new chronic pain classification were approved in 2019 and will come into effect on January 1, 2022. While the implementation of the ICD-11 in national health systems will take time, clinicians and researchers are encouraged to begin using the new chronic pain diagnoses. They are available online at https://icd.who.int/browse11/l-m/en.
The new classification was overdue. In previous versions of the ICD, many chronic pain diagnoses were poorly defined and scattered among a variety of chapters; others were missing altogether (eg, chronic cancer pain and chronic neuropathic pain).[51,52] It is expected that the ICD-11 chronic pain section will make epidemiological studies easier, increase the visibility of chronic pain on international and national health agendas, and facilitate treatment pathways and research. The new classification is based on scientific evidence and reflects the biopsychosocial model of chronic pain. Pain is defined, according to the updated IASP definition, as "unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage." Chronic pain is pain that recurs or persists for more than 3 months.[60,61] The ICD-11 classification of chronic pain consists of 7 main categories.[1,7,8,44,48,56,57] Chronic primary pain, in which chronic pain is considered a health problem in its own right, is distinguished from 6 categories of chronic secondary pain. In chronic secondary pain, the pain is regarded as a symptom of an underlying disease. The categories of chronic secondary pain are as follows: MG30.1 Chronic cancer-related pain, MG30.2 chronic postsurgical or post traumatic pain, MG30.3 Chronic secondary musculoskeletal pain, MG30.4 Chronic secondary visceral pain, MG30.5 Chronic neuropathic pain, and MG30.6 Chronic secondary headache or orofacial pain.
The chronic pain section of the ICD-11 provides operationalized diagnostic criteria for each diagnosis. Optional extension codes are available for all types of pain to document chronic pain intensity, pain-related distress, pain-related interference, the temporal course of the pain, and the presence of psychosocial factors associated with the pain.[60,76] Existing classifications such as the ROME-IV criteria for Functional Gastrointestinal Disorders or the International Classification of Headache Disorders (ICHD-3) were integrated within the ICD-11 chronic pain classification. First field tests provide evidence for the validity, reliability, and clinical utility of the ICD-11 chronic pain classification.[3,4,36]
Users beginning to apply the ICD-11 chronic pain classification in clinical practice or research are likely to encounter questions regarding the new diagnoses or their intended uses. Several of these questions reached the IASP TF in the past couple of years, eg, at conferences, by letter, or during field testing. With this publication, we hope to provide guidance on the most frequently asked questions, hence facilitating the implementation of the new diagnoses in clinical practice and research.
Pain. 2022;163(9):1675-1687. © 2022 Lippincott Williams & Wilkins