Evaluation of sweating responses in patients with collagen disease using the quantitative sudomotor axon reflex test (QSART): A study protocol for an investigator-initiated, prospective, observational clinical study

Introduction Sweat secretion is controlled by the sympathetic nervous system and is less active during winter than in the summer. Raynaud's phenomenon is affected by an excessive strain of the sympathetic nerves after exposure to a cold environment, thus reducing the quality of life of patients with collagen disease. Herein, we focus on the eccrine sweat glands that receive both adrenergic and cholinergic innervation. Our hypothesis is that excessive activation of sympathetic nerve in Raynaud's phenomenon can affect sweating, especially in winter. This study is designed to evaluate the neuroactive sweating responses in patients with collagen disease and to assess its association with skin findings in peripheral circulatory disorders. Methods and analysis The study will be conducted at a single centre in Japan. Patients with systemic sclerosis, Sjogren's syndrome, systemic lupus erythematosus, mixed connective tissue disease, and dermatomyositis will be assessed using the quantitative sudomotor axon reflex test. The primary outcomes will be sweat volume and reaction time due to axon reflex and the Raynaud's condition score. The secondary outcomes will include patient background, skin symptoms (digital ulcers, pernio-like eruptions, subcutaneous calcifications, telangiectasia, nailfold capillary dilatation/bleeding and degree of skin sclerosis) and skin surface temperature. Evaluation will be done two times, during the summer and winter, allowing for the assessment of seasonal differences in sweating responses. Ethics and dissemination Ethical approval of this study was certified by the clinical research review board of Nagasaki University Hospital (Reference number: CRB19-001). We will disseminate the findings of this study through peer-reviewed publications and conference presentations. Trial registration number jRCTs072190009; pre-results.