Prevalence, incidence, and associated factors of avascular necrosis in Korean patients with systemic lupus erythematosus: a nationwide epidemiologic study.

Avascular necrosis (AVN) is one of the most frequent types of organ damage in systemic lupus erythematosus (SLE). However, little is currently known about the epidemiology of AVN in SLE patients. The aim of this study was to estimate the prevalence and incidence of AVN in Korean patients with SLE based on National Health Insurance (NHI) claims data and to determine the risk factors for AVN among SLE patients. This study was conducted using the 2006-2010 data of 25,358 SLE patients from the NHI program. AVN cases were defined as those with at least one diagnosis of AVN. The prevalence was calculated by dividing the number of AVN cases by the number of SLE cases in the same year. The annual incidence was calculated by dividing the number of incident AVN cases by the number of SLE-prevalent cases not previously diagnosed with AVN. Patients who developed AVN in 2008-2010 were compared with SLE patients who did not develop AVN to identify any risk factors. The prevalence of AVN among SLE patients (2006-2010) was 31.5-34.2 per 1,000 persons and was similar in all the years studied. The incidence per 1,000 persons of AVN among SLE patients was 8.6 [95 % confidence interval (95 % CI) 6.9-10.3] in 2008, 9.8 (95 % CI 8.0-11.6) in 2009, and 8.4 (95 % CI 6.8-10.0) in 2010. Regression analysis indicated that taking an oral corticosteroid [odds ratio (OR) 2.12, 95 % CI 1.39-3.23] or an intravenous corticosteroid (OR 1.5, 95 % CI 1.2-1.89) was significantly associated with AVN. In addition, AVN was associated with use of immunosuppressive agents (OR 2.12, 95 % CI 1.66-2.72), hydroxychloroquine (OR 1.4, 95 % CI 1.09-1.81), and lipid-lowering agents (OR 1.78, 95 % CI 1.24-2.57) among the prescribed medications, and with hypertension (OR 1.39, 95 % CI 1.08-1.79) among the comorbidities. The prevalence and incidence of AVN among SLE patients, which were 31.5-34.2 and 8.4-9.8 per 1,000 persons, respectively, may be representative of the entire population of symptomatic AVN patients with SLE in Korea. AVN is associated with the use of corticosteroids, immunosuppressants, hydroxychloroquine, lipid-lowering agents, and with hypertension. Studies of large, prospective cohorts are needed to confirm these results.