Objective. To perform a genome-wide association study (GWAS) in Koreans in order to identify susceptibility loci for rheumatoid arthritis (RA).Methods. We generated high-quality genotypes for 441,398 single-nucleotide polymorphisms (SNPs) in 801 RA cases and 757 controls. We then tested 79 markers from 46 loci for replication in an independent sample of 718 RA cases and 719 controls.Results. Genome-wide significance (P < 5 ؋ 10 -08 ) was attained by markers from the major histocompatibility complex region and from the PADI4 gene. The replication data showed nominal association signals (P < 5 ؋ 10 -02

This study aimed to develop an identification algorithm for validating the International Classification of Diseases-Tenth diagnostic codes for rheumatoid arthritis (RA) in the Korean National Health Insurance (NHI) claims database. An individual copayment beneficiaries program for rare and intractable diseases, including seropositive RA (M05), began in South Korea in July 2009. Patients registered in this system pay only 10 % of their total medical costs, but registration requires an official report from a doctor documenting that the patient fulfills the 1987 ACR criteria. We regarded patients registered in this system as gold standard RA and examined the validity of several algorithms to define RA diagnosis using diagnostic codes and prescription data. We constructed nine algorithms using two highly specific prescriptions (positive predictive value >90 % and specificity >90 %) and one prescription with high sensitivity (>80 %) and accuracy (>75 %). A total of 59,823 RA patients were included in this validation study. Among them, 50,082 (83.7 %) were registered in the individual copayment beneficiaries program and considered true RA. We tested nine algorithms that incorporated two specific regimens [biologics and leflunomide alone, methotrexate plus leflunomide, or more than 3 disease-modifying anti-rheumatic drugs (DMARDs)] and one sensitive drug (any non-steroidal anti-inflammatory drug (NSAID), any DMARD, or any NSAID plus any DMARD). The algorithm that included biologics, more than 3 DMARDs, and any DMARD yielded the highest accuracy (91.4 %). Patients with RA diagnostic codes with prescription of biologics or any DMARD can be considered as accurate cases of RA in Korean NHI claims database.

Recently, two studies provided convincing evidence that IFN regulatory factor 5 (IRF5) gene polymorphisms are significantly associated with systemic lupus erythematosus (SLE) in several white populations. To replicate the association with SLE in an Asian population, we examined the genetic effects in our SLE cohort from a Korean population. A total of 1,565 subjects, composed of 593 cases and 972 controls, were genotyped using the TaqMan® (Applied Biosystems, Foster City, CA, USA) method. The genetic effects of polymorphisms on the risk of SLE were evaluated using χ2 tests and a Mantel–Haenszel meta-analysis. Statistical analysis revealed results in the Korean population were similar to the previous reports from white populations. The rs2004640 T allele had a higher frequency in SLE cases (0.385) than controls (0.321; odds ratio (OR) = 1.32, P = 0.0003). In combined analysis, including all seven independent cohorts from the three studies so far, robust and consistent associations of the rs2004640 T allele with SLE were observed. The estimate of risk was OR = 1.44 (range, 1.34–1.55), with an overall P = 1.85 × 10-23 for the rs2004640 T allele. The haplotype (rs2004640T–rs2280714T) involved in both the alternative splice donor site and the elevated expression of IRF5 also had a highly significant association with SLE (pooled, P = 2.11 × 10-16). Our results indicate that the genetic effect on the risk of SLE mediated by IRF5 variants can be generally accepted in both white and Asian populations.

The objectives of this study are to identify the prevalence and incidence of rheumatoid arthritis (RA) and to investigate the patterns of medical care and drug utilization by RA patients in Korea. Korean National Health Insurance claims data were used for analysis. RA patients were defined as those having an RA code from 2009 to 2012 and using disease-modifying anti-rheumatic drugs (DMARDs) within 1 year after the code. RA patients identified in 2010 with a disease-free period for 12 months before the index date, and those who received continuous treatment in 2011-2013 were defined as incident cases. Patterns of medical care and drug utilization were compared among subgroups. The prevalence of RA increased yearly from 0.28% in 2009 to 0.32% in 2012. The incidence of RA in 2010 was 28.5 per 100,000 person-years. The use of biologic DMARDs (bDMARDs) increased from 2.31% in 2009 to 4.05% in 2012. Hydroxychloroquine (57.53-62.45%) was the most commonly used the conventional DMARDs, followed by methotrexate (49.99-51.87%). The use of bDMARDs (1.39 vs. 2.43%) was less frequent in EORA patients than YORA patients. Hydroxychloroquine (74.96 vs. 72.11%) was more frequently used, but methotrexate (55.24 vs. 59.25%) and sulfasalazine (27.96 vs. 32.72%) were used less frequently in EORA patients than in YORA patients. The prevalence of RA has increased in Korea. EORA patients used fewer bDMARDs, methotrexate, and sulfasalazine but more hydroxychloroquine than YORA patients.

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