@article {Bottaie000507, author = {Matteo Bottai and Anna Tj{\"a}rnlund and Giola Santoni and Victoria P Werth and Clarissa Pilkington and Marianne de Visser and Lars Alfredsson and Anthony A Amato and Richard J Barohn and Matthew H Liang and Jasvinder A Singh and Rohit Aggarwal and Snjolaug Arnardottir and Hector Chinoy and Robert G Cooper and Katalin Danko and Mazen M Dimachkie and Brian M Feldman and Ignacio Garc{\'\i}a-De La Torre and Patrick Gordon and Taichi Hayashi and James D Katz and Hitoshi Kohsaka and Peter A Lachenbruch and Bianca A Lang and Yuhui Li and Chester V Oddis and Marzena Olesinka and Ann M Reed and Lidia Rutkowska-Sak and Helga Sanner and Albert Selva-O{\textquoteright}Callaghan and Yeong Wook Song and Jiri Vencovsky and Steven R Ytterberg and Frederick W Miller and Lisa G Rider and Ingrid E Lundberg}, editor = {, and Amoruso, Maria and Andersson, Helena and Bayat, Nastaran and Bhansing, Kavish J and Bucher, Sara and Champbell, Richard and Charles-schoeman, Christina and Chaudhry, Vinay and Christopher-stine, Lisa and Chung, Lorinda and Cronin, Mary and Curry, Theresa and Dahlbom, Kathe and Distler, Oliver and Efthimiou, Petros and Van engelen, Baziel Gm and Faiq, Abdullah and Farhadi, Payam Noroozi and Fiorentino, David and Hengstman, Gerald and Hoogendijk, Jessica and Huber, Adam and Kataoka, Hiroshi and Katsumata, Yasuhiro and Kim, Susan and Kong-rosario, Michelle and Kontzias, Apostolos and Krol, Petra and Kurita, Takashi and Li, Zhan-guo and Lindvall, Bj{\"o}rn and Linklater, Helen and Maillard, Sue and Mamyrova, Gulnara and Mantegazza, Renato and Marder, Galina S and Nagahashi marie, Suely Kazue and Mathiesen, Pernille and Mavragani, Clio P and Mchugh, Neil J and Michaels, Mimi and Mohammed, Reem and Morgan, Gabrielle and Moser, David W and Moutsopoulos, Haralampos M}, title = {EULAR/ACR classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups: a methodology report}, volume = {3}, number = {2}, elocation-id = {e000507}, year = {2017}, doi = {10.1136/rmdopen-2017-000507}, publisher = {BMJ Specialist Journals}, abstract = {Objective To describe the methodology used to develop new classification criteria for adult and juvenile idiopathic inflammatory myopathies (IIMs) and their major subgroups.Methods An international, multidisciplinary group of myositis experts produced a set of 93 potentially relevant variables to be tested for inclusion in the criteria. Rheumatology, dermatology, neurology and paediatric clinics worldwide collected data on 976 IIM cases (74\% adults, 26\% children) and 624 non-IIM comparator cases with mimicking conditions (82\% adults, 18\% children). The participating clinicians classified each case as IIM or non-IIM. Generally, the classification of any given patient was based on few variables, leaving remaining variables unmeasured. We investigated the strength of the association between all variables and between these and the disease status as determined by the physician. We considered three approaches: (1) a probability-score approach, (2) a sum-of-items approach criteria and (3) a classification-tree approach.Results The approaches yielded several candidate models that were scrutinised with respect to statistical performance and clinical relevance. The probability-score approach showed superior statistical performance and clinical practicability and was therefore preferred over the others. We developed a classification tree for subclassification of patients with IIM. A calculator for electronic devices, such as computers and smartphones, facilitates the use of the European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria.Conclusions The new EULAR/ACR classification criteria provide a patient{\textquoteright}s probability of having IIM for use in clinical and research settings. The probability is based on a score obtained by summing the weights associated with a set of criteria items.}, URL = {https://rmdopen.bmj.com/content/3/2/e000507}, eprint = {https://rmdopen.bmj.com/content/3/2/e000507.full.pdf}, journal = {RMD Open} }