Development and Testing of a Hybrid Measure of Muscle Strength in Juvenile Dermatomyositis for Use in Routine Care |
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| Authors: | Giulia Camilla Varnier Silvia Rosina Cristina Ferrari Angela Pistorio Alessandro Consolaro Francesca Bovis Sara Dalprà Clarissa Pilkington Susan Maillard Adele Civino Elena Tsitsami Jaime de Inocencio Marija Jelusic Jelena Vojinovic Graciela Espada Balahan Makay Maria Martha Katsicas Polixeni Pratsidou‐Gertsi Dragana Lazarevic Anand Prahalad Rao Denise Pires Marafon Nicolino Ruperto Alberto Martini Angelo Ravelli |
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| Institution: | 1. Università degli Studi di Genova, Genoa, Italy;2. Istituto Giannina Gaslini, Genoa, Italy;3. Università degli Studi di Genova and Istituto Giannina Gaslini, Genoa, Italy;4. Great Ormond Street Hospital, London, UK;5. Ospedale Vito Fazzi, Lecce, Italy;6. Children's Hospital Agia Sofia, Athens, Greece;7. Hospital Universitario 12 de Octubre, Madrid, Spain;8. University Hospital Center Zagreb, Zagreb, Croatia;9. University of Ni?, Ni?, Serbia;10. Hospital de Ni?os Ricardo Gutiérrez, Buenos Aires, Argentina;11. Dokuz Eylül University Hospital, Izmir, Turkey;12. Hospital de Pediatría Juan P. Garrahan, Buenos Aires, Argentina;13. Hippokration General Hospital, Thessaloniki, Greece;14. Clinic Center, Ni?, Serbia;15. Manipal Hospital, Bangalore, India;16. Ospedale Pediatrico Bambino Gesù, Rome, Italy |
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| Abstract: | Objective To develop and test a hybrid measure of muscle strength for juvenile dermatomyositis (JDM), which is based on the combination of the Manual Muscle Testing in 8 muscles (MMT‐8) and the Childhood Myositis Assessment Scale (CMAS) but is more comprehensive than the former and more feasible than the latter. Methods The hybrid MMT‐8/CMAS (hMC) is composed of all 8 items of the MMT‐8 and 3 items of the CMAS: time of head lift, assessment of abdominal muscles, and floor rise. The score ranges 0–100, with 100 indicating normal muscle strength. Validation procedures were conducted using 3 large multinational patient samples, including a total of 810 JDM patients. Results The hMC revealed face and content validity, good construct validity, excellent test–retest reliability (intraclass correlation coefficient = 0.99), and internal consistency (Cronbach's α = 0.94), strong responsiveness to clinical change over time (standardized response mean = 0.8 among patients judged as improved by the caring physician), and satisfactory capacity to discriminate patients judged as being in the states of inactive disease or low, moderate, or high disease activity by the physician (P < 0.001) or patients whose parents were satisfied or not satisfied with the illness course (P < 0.001). Conclusion The hMC was found to possess good measurement properties in a large population of patients with a wide range of disease activity and severity. The new tool, which is primarily intended for use in routine clinical care, should be further tested in other populations of patients evaluated prospectively. |
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