Prevalence of Systemic Lupus Erythematosus in South Korea: An Administrative Database Study

Background: Systemic lupus erythematosus (SLE) is a rare autoimmune disease for which a population-based survey on the prevalence of the disease in South Korea has not yet been conducted. Our goal was to estimate the nationwide prevalence of SLE. Methods: The International Classification of Diseases, Tenth Revision (ICD-10) code for SLE diagnosis-M32- was tentatively given when patients were suspected to have SLE before 2009. As such, the positive predictive value (PPV) of the M32 code shown in medical bills reflecting true SLE was uncertain. We attempted to estimate the prevalence of SLE in South Korea using national administrative database data from 2004-2006. We approximated the actual number of SLE patients by analyzing a list of SLE-coded patients provided by the National Health Insurance (NHI) and Health Insurance Review and Assessment Service. Prevalence was estimated by multiplying the PPV of the M32 diagnostic code by the number of patients receiving the code. The PPV was determined by three methods: direct investigation of the medical records of patients randomly selected from the SLE-coded patients list; assessment of all SLE patients treated at 56 selected hospitals in South Korea; and extrapolation from sub-groups at a single institute to the sub-groups of the national NHI data. Results: The estimated number of national SLE cases was between 9000 and 11 000, depending on the method of ascertainment, corresponding to a prevalence of 18.8-21.7 per 100 000 people. Conclusions: This is the first report of a nationwide prevalence survey of SLE in South Korea. National databases may serve as a resource for epidemiologic studies of rare autoimmune diseases like SLE.