Internationale Feldstudien zur Evaluation der Klassifikation chronischer Schmerzen in der 11. Revision der Internationalen statistischen Klassifikation der Krankheiten und verwandter Gesundheitsprobleme (ICD-11)

The 11th revision of the International Classification of Diseases and Related Health Problems (ICD-11) will come into effect worldwide on January 1st, 2022. The ICD-11 has many different applications, including clinical documentation, reimbursement of medical services, public health decisions as well as mortality and morbidity statistics. Despite high prevalence rates and a significant disease burden, chronic pain is not represented adequately in the current 10th revision of the ICD (ICD-10). Therefore, a comprehensive classification of chronic pain, which defines seven main categories of chronic pain, was developed for the ICD-11. Diagnostic classification systems should meet different psychometric criteria, including validity and reliability. Validity and reliability, in turn, are important prerequisites for the clinical utility of a classification system. The improvement of clinical utility as well as global applicability were defined as main goals of the ICD revision process. The overall aim of the present doctoral thesis was the evaluation of the ICD-11 classification of chronic pain in international formative and evaluative field studies. Formative field studies are conducted during the development of a classification system to enable necessary adjustments of its overall structure. Therefore, study 1 aimed at evaluating the main categories of the ICD-11 chronic pain classification in a formative field study. The study was implemented in routine clinical care in pain clinics as well as primary care clinics in Australia, Germany, Japan, and Norway. Results showed that the seven main categories accounted for 97 % of chronic pain syndromes. Only 2 % of the chronic pain syndromes were allocated to more than one category. With the exhaustiveness of capturing all underlying pain syndromes and the mutual exclusiveness of the categories, the new classification fulfils two important psychometric criteria of diagnostic classification systems. A further formative field study (study 2) aimed at evaluating whether the new classification can be integrated within the overall structure of the ICD-11, and whether the coding rules as defined by the World Health Organization (WHO) can be applied to the new chronic pain diagnoses. An online field study was conducted internationally. Pain specialists assigned ICD-10 and ICD-11 diagnoses to diagnostic statements. Furthermore, they assigned ICD-11 diagnoses to brief case vignettes. The ICD-11 diagnoses performed better than the ICD-10 diagnoses with regard to correct code assignment, ease of use, level of detail, and ambiguity. The coding rules were applied correctly to the majority of case vignettes. The clinical utility of the new diagnoses was rated as very high. In order to facilitate the application of the classification as well as to standardize code assignment in research and in clinical practice, a classification algorithm was developed (study 3). In a pilot evaluation, pain specialists evaluated the algorithm with regard to its utility. The overall structure of the algorithm, which is a linear decision tree, conforms with internationally established guidelines. When following the boxes and arrows consequently, the algorithm leads users to the ICD-11 chronic pain diagnoses that apply. Hyperlinks and page references facilitate the use of the pdf document. In the pilot evaluation, the algorithm was rated as very useful. In addition to the formative field studies (studies 1 and 2), an extensive international evaluative field study was conducted as well, as part of the present doctoral thesis (study 5). First, the study protocol for an ecological implementation field study was developed (study 4). The study protocol defines two phases of data collection, which will be implemented in countries of all income groups. Participants will assign the new ICD-11 chronic pain diagnoses to consecutive patients. The inter-rater reliability as well as ratings of their clinical utility are the main outcomes of the study. Study 5 implemented this study protocol in pain clinics in India (lower-middle-income country), Cuba (high-middle-income country), and New Zealand (high-income country). Inter-rater reliability was computed for 11 diagnoses. For 10 of these diagnoses, inter-rater reliability was substantial. The clinical utility of the new diagnoses was rated as very high. In conclusion, the present doctoral thesis provides findings of the high quality of the new ICD-11 chronic pain classification. The classification was applicable globally in the present field studies. Therefore, the new classification meets the main goals of the ICD-11.