Patients and Data Collection
The study subjects were patients diagnosed as ‘gout’ or ‘gouty arthritis’ in the electronic medical record system, and were treated in the inpatient department, of The First Affiliated Hospital of Zhejiang Chinese Medical University from May 2018 to May 2020. They came from all over Zhejiang province in China. They were deemed included if they had fulfilled the Gout Diagnostic Criteria formulated by the American College of Rheumatology (ACR)13 or the 2015 Gout Classification Criteria by the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR).14 Patients diagnosed as secondary gout that caused by kidney or myeloproliferative diseases, or combined with other forms of arthritis such as osteoarthritis or rheumatoid arthritis were excluded. Tophi diagnosis was determined by rheumatologist or endocrinologist as draining or chalk-like subcutaneous nodules under transparent skin, often with overlying vascular and present around joints, ears, olecranon bursae, finger pads or tendons, based on the 2015 ACR/EULAR Gout Classification Criteria.14 For patients who had been admitted to the hospital more than once during the study period, only the data from the first admission were analysed. Research approval was obtained from the hospital’s Ethics Committee (approval no.2020-KL-127-01), and all study subjects were fully informed consents.
One hundred and fifty-eight gout patients were included in the study, and were classified as either ‘tophi group’ or ‘non-tophi group’ for analysis. Twenty-two variables, such as demographics and disease and treatment characteristics of the patients, were manually collected from the hospital’s electronic medical record system (Table 1) . According to the result of a large sample size study of the clinical characteristics associated with Chinese tophaceous gout patients and previous clinical experience, we chose 45 years old, 10 years, 3 joints and 360 umol/l as respective cut point for onset age, disease duration, number of joint involved and serum uric acid level.2