Study design
To protect individual privacy, the original identification numbers of the beneficiaries’ data were encrypted for privacy. Encryption procedures were consistent with other datasets and ensured that all claims data could be linked in order to obtain additional medically relevant data. All data that could be used to identify patients or care providers, including the names of medical institutions and physicians, were encrypted. Patients with RA (the international classification of diseases, ninth revision (ICD-9) with 714.0) in the LHID 2005 were initially screened. We confirmed RA diagnosis using catastrophic illness certification (CIC) according to the NHI program regulations [3, 4]. Therefore, all RA diagnoses required the agreement of two rheumatologists, one application rheumatologist and one anonymous senior rheumatologist as the reviewer. All rheumatologists met the following two criteria: three-year internal medicine residents training in a quality hospital, usually a tertiary hospital, and two-year rheumatology fellow training. “Senior” usually refers to a rheumatologist career that has spanned at least 10 years.