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Objective: The objective of this study was to assess the effectiveness of tofacitinib vs TNF inhibitors (TNFis) in Korean patients with RA., Methods: The study used data from a single academic referral hospital's registries of biologic DMARDs (bDMARDs) and tofacitinib and examined remission rates based on the DAS28-ESR after 12 months. Multivariable logistic regression analysis was used to estimate the odds ratio (OR) for achieving remission with tofacitinib compared with TNFi, adjusting for potential confounders., Results: This analysis included 665 patients (200 on tofacitinib and 455 on TNFis) who were followed up for at least 12 months. Of these, 96 patients in the tofacitinib group (48.0%) and 409 patients in the TNFi group (89.9%) were treatment-naïve to bDMARDs. Intention-to-treat analysis revealed no significant difference in the remission rates between the two groups (18.0% vs 19.6%, P = 0.640). Multivariable analysis demonstrated comparable remission rates with tofacitinib and TNFi (OR 1.204, 95% CI 0.720-2.013). In the subpopulation naïve to Janus kinase inhibitors (JAKis) and bDMARDs, tofacitinib showed better remission rates than TNFis (OR 1.867, 95% CI 1.033-3.377). Tofacitinib had more adverse events but similar rates of serious adverse events to TNFis., Conclusion: In real-world settings, there was no significant difference in remission rates at 12 months between the tofacitinib and TNFi groups. In terms of safety, tofacitinib exhibited a higher incidence of adverse events compared with TNFis, while the occurrence of serious adverse events was comparable between the groups., Trial Registration: ClinicalTrials.gov, https://clinicaltrials.gov, NCT02602704., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objective: Anti-TNF biologics have been widely used to ameliorate disease activity in patients with RA. However, a large fraction of patients show a poor response to these agents. Moreover, no clinically applicable predictive biomarkers have been established. This study aimed to identify response-associated biomarkers using longitudinal transcriptomic data in two independent RA cohorts., Methods: RNA sequencing data from peripheral blood cell samples of Korean and Caucasian RA cohorts before and after initial treatment with anti-TNF biologics were analysed to assess treatment-induced expression changes that differed between highly reliable excellent responders and null responders. Weighted correlation network, immune cell composition, and key driver analyses were performed to understand response-associated transcriptomic networks and cell types and their correlation with disease activity indices., Results: In total, 305 response-associated genes showed significantly different treatment-induced expression changes between excellent and null responders. Co-expression network construction and subsequent key driver analysis revealed that 41 response-associated genes played a crucial role as key drivers of transcriptomic alteration in four response-associated networks involved in various immune pathways: type I IFN signalling, myeloid leucocyte activation, B cell activation, and NK cell/lymphocyte-mediated cytotoxicity. Transcriptomic response scores that we developed to estimate the individual-level degree of expression changes in the response-associated key driver genes were significantly correlated with the changes in clinical indices in independent patients with moderate or ambiguous response outcomes., Conclusion: This study provides response-specific treatment-induced transcriptomic signatures by comparing the transcriptomic landscape between patients with excellent and null responses to anti-TNF drugs at both gene and network levels., (© The Author(s) 2023. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objectives: We aimed to investigate medication utilisation trends during pregnancy and identify factors associated with adverse pregnancy outcomes (APOs) in patients with rheumatoid arthritis (RA)., Methods: Female patients with RA aged 20-50 years were identified from the Korean national health insurance database between 2010 and 2020. Pregnancy episodes were divided into two groups according to pregnancy outcome: the delivery group and the APO group (abortion and stillbirth). The characteristics and medication utilisation patterns were compared between the two groups, and multivariable logistic regression analysis was conducted to identify the factors associated with APOs., Results: A total of 5728 pregnancy episodes were included, comprising 4576 delivery episodes and 1152 APO episodes. The mean maternal age for all pregnancy episodes was 33.7 years; 33.3 years in the delivery group and 33.7 years in the APO group. Hydroxychloroquine was the most commonly used conventional synthetic disease-modifying antirheumatic drug (DMARD) during the preconception period and pregnancy in both groups. The prescription rate of all DMARDs decreased rapidly during pregnancy. In the multivariable analysis, use of methotrexate (adjusted OR (aOR): 2.14, 95% CI 1.57 to 2.92) and leflunomide (aOR: 2.68, 95% CI 1.39 to 5.15) within 3 months before conception was associated with APOs., Conclusion: Methotrexate and leflunomide are associated with an increased possibility of APOs, emphasising the importance of appropriate medication adjustment when planning for pregnancy., Competing Interests: Competing interests: Y-KS has received research grants from Bristol-Myers Squibb, Eisai, Pfizer and JW Pharmaceutical. DHY has received research grants from Celltrion, has served as an outside board of Celltrion and is on the speakers’ bureau of Celltrion and Celltrion Healthcare., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: There was a safety concern about an increased risk of thromboembolic events in patients with rheumatoid arthritis (RA) treated with Janus kinase inhibitors (JAKis). This study aimed to determine the risk of venous thromboembolism (VTE) in Korean patients with RA treated with JAKis compared with tumour necrosis factor (TNF) inhibitors., Methods: Using the National Health Insurance Service database between 2015 and 2019, patients with prevalent RA who started JAKi or TNF inhibitor were selected as the study population. All participants were naïve to targeted therapy. Patients that had experienced any VTE event or used anticoagulant agents within 30 days were excluded. Demographic and clinical characteristics were all balanced by stabilised inverse probability of treatment weighting (sIPTW) using propensity score. The Cox proportional hazard model considering death as a competing risk was used to evaluate the risk of VTE in JAKi users compared with TNF inhibitor users., Results: A total of 4,178 patients were included: 871 JAKi users and 3,307 TNF inhibitor users were followed up for 1,029.2 person-years (PYs) and 5,940.3 PYs, respectively. With a balanced sample after sIPTW, the incidence rates (IR) of VTE were 0.06 per 100 PYs (95% confidence interval [CI] 0.00-1.23) in JAKi users and 0.38 per 100 PYs (95% CI 0.25-0.58) in TNF inhibitor users. The hazard ratio was 0.18 (95% CI 0.01-3.47) after adjusting for unbalanced variables after performing sIPTW., Conclusion: There is no increased risk of VTE in RA patients treated with JAKis compared with TNF inhibitors in Korea., Competing Interests: Declaration of Competing Interest YKS has received research grants from Bristol-Myers Squibb, Eisai, Pfizer, and JW Pharmaceutical. Other authors declare that there are no conflicts of interest., (Copyright © 2023. Published by Elsevier Inc.)

Background/aims: We aimed to compare the effectiveness and safety of Janus kinase inhibitors (JAKi) vs. biologic disease- modifying antirheumatic drugs (bDMARD) in Korean patients with rheumatoid arthritis (RA) who had an inadequate response to conventional synthetic DMARDs., Methods: A quasi-experimental, multi-center, prospective, non-randomized study was conducted to compare response rates between JAKi and bDMARDs in patients with RA naïve to targeted therapy. An interim analysis was performed to estimate the proportion of patients achieving low disease activity (LDA) based on disease activity score (DAS)-28- erythroid sedimentation rate (ESR) (DAS28-ESR) at 24 weeks after treatment initiation and to evaluate the development of adverse events (AEs)., Results: Among 506 patients enrolled from 17 institutions between April 2020 and August 2022, 346 (196 JAKi group and 150 bDMARD group) were included in the analysis. After 24 weeks of treatment, 49.0% of JAKi users and 48.7% of bDMARD users achieved LDA (p = 0.954). DAS28-ESR remission rates were also comparable between JAKi and bDMARD users (30.1% and 31.3%, respectively; p = 0.806). The frequency of AEs reported in the JAKi group was numerically higher than that in the bDMARDs group, but the frequencies of serious and severe AEs were comparable between the groups., Conclusion: Our interim findings reveal JAKi have comparable effectiveness and safety to bDMARDs at 24 weeks after treatment initiation.

We aimed to determine the risk of herpes zoster (HZ) in Korean rheumatoid arthritis (RA) patients on tofacitinib compared with tumor necrosis factor inhibitor (TNFi) treatment. From the prospective cohorts of RA patients who started tofacitinib or TNFi in an academic referral hospital in Korea, patients who started tofacitinib between March 2017 and May 2021 and those who started TNFi between July 2011 and May 2021 were included. Baseline characteristics of tofacitinib and TNFi users were balanced through inverse probability of treatment weighting (IPTW) using the propensity score including age, disease activity of RA and medication use. The incidence rate of HZ in each group and incidence rate ratio (IRR) were calculated. A total of 912 patients were included: 200 tofacitinib and 712 TNFi users. There were 20 cases of HZ among tofacitinib users and 36 among TNFi users during observation period of 331.4 person-years (PYs) and 1950.7 PYs, respectively. In IPTW analysis with a balanced sample, IRR of HZ was 8.33 (95% confidence interval 3.05-22.76). Tofacitinib use increased the risk of HZ compared with TNFi in Korean patients with RA, but the rate of serious HZ or permanent discontinuation of tofacitinib due to HZ event was low., (© 2023. The Author(s).)

Objective: Deciding which drug to choose for targeted therapy is an important step in sequential treatment for rheumatoid arthritis (RA). This study aimed to identify factors for selecting Janus kinase inhibitors (JAKis) rather than biologic disease-modifying antirheumatic drugs (bDMARDs) in patients with RA in real-world practice., Methods: We selected RA patients starting JAKis or bDMARDs from single-center prospective cohorts in Korea. Patients were divided into JAKi, tumor necrosis factor (TNF) inhibitor, and non-TNF inhibitor groups. We performed multinomial logistic regression analyses to identify factors associated with selecting JAKis., Results: 145, 205, and 89 patients were included in the JAKi, TNF inhibitor, and non-TNF inhibitor groups. In multinomial regression analysis, the JAKi group was older than the TNF inhibitor group (OR 1.03, 95% confidence interval [CI] 1.01-1.05) but younger than the non-TNF inhibitor group (OR 0.97, CI 0.95-1.00). The JAKi group was less likely to have chronic pulmonary diseases compared with the TNF inhibitor group (OR 0.07, CI 0.01-0.56) or the non-TNF inhibitor group (OR 0.06, CI 0.01-0.50). Higher disease activity assessed by physician (OR 1.80, CI 1.51-2.38) and previous tacrolimus use (OR 2.05, CI 1.20-3.51) were factors suggesting selection of JAKis than TNF inhibitors., Conclusion: Age, pulmonary comorbidities, previous tacrolimus use, and high disease activity assessed by physician were factors influencing the selection of JAKis for RA patients in Korea., Competing Interests: DHY has received research grants from Celltrion, has served as a consultant for Celltrion, and is on the speakers’ bureau of Celltrion and Celltrion Healthcare. YKS has received research grants from Bristol-Myers Squibb, Eisai, Pfizer, and JW Pharmaceutical. There are no patents, and no products in development or being marketed to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials. Other authors declare no conflicts of interest., (Copyright: © 2023 Song et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objective: To determine the risk of malignancy in Korean patients with rheumatoid arthritis (RA) receiving Janus kinase inhibitors (JAKis) compared with tumour necrosis factor inhibitors (TNFis)., Methods: A retrospective cohort of patients with RA initiating their first JAKi or TNFi was established using the Korean National Health Insurance database between 2015 and 2019. They were followed up from treatment initiation to the occurrence of malignancy, drug discontinuation, death or until December 2019. Baseline features of the patients were balanced through inverse probability of treatment weighting (IPTW) using a propensity score. A Cox proportional hazard model was established to estimate the HR for malignancy risk in JAKi users compared with TNFi users., Results: A total of 4929 patients (1064 JAKi-treated and 3865 TNFi-treated patients) were included, and the observation periods were 1288.6 person-years (PYs) for JAKi users and 6823.8 PYs for TNFi users. The incidence rates of overall malignancy were 0.54 per 100 PYs (95% CI 0.26 to 1.14) in JAKi users and 0.85 per 100 PYs (95% CI 0.66 to 1.10) in TNFi users. In IPTW analysis with a balanced sample (4101 JAKi-treated and 5131 TNFi-treated patients), HR was 0.83 (95% CI 0.55 to 1.27) for overall malignancy: 0.77 (95% CI 0.50 to 1.19) for solid malignancy and 2.86 (95% CI 0.41 to 20.00) for haematological malignancy., Conclusion: Malignancy risk in Korean patients with RA was not increased with JAKi use compared with TNFi use., Competing Interests: Competing interests: Y-KS has received research grants from Bristol-Myers Squibb, Eisai, Pfizer and JW Pharmaceutical. Other authors declare no conflict of interest., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: We aimed to examine the uptake of infliximab and etanercept biosimilars in patients with rheumatoid arthritis (RA) and its economic implication for healthcare expenditure., Methods: Using Korean Health Insurance Review and Assessment Service National Patient Samples, we extracted RA patients who used biologic disease modifying anti-rheumatic drugs (bDMARDs) between 2009 and 2018. Descriptive statistics were used to explain the basic features of the data. We calculated the proportion of users of each bDMARD among total patients with bDMARDs half-yearly. We assessed changes in the utilization proportions of bDMARDs including 4 tumor necrosis factor inhibitors (TNFis) and 2 non-TNFis, which have been approved for RA in Korea: etanercept, infliximab, adalimumab, golimumab, tocilizumab, and abatacept, and analyzed the changes in market share of biosimilars among the bDMARDs after their introduction. Overall trends of medical costs for each bDMARD were presented over the 10-year period., Results: Since the introduction of the biosimilar TNFis in 2012, the proportion of their use among bDMARDs steadily increased to 15.8% in 2018. While there has been a gradual increase in the use of biosimilar TNFis, the use of the corresponding originators has been decreasing. The introduction of biosimilar TNFis has resulted in a decrease in the medical costs of patients using either originator or biosimilar TNFis., Conclusion: In Korea, the proportional use of biosimilar TNFis has gradually increased since their introduction. The availability of less expensive biosimilar TNFis seems to have brought about a decrease in the medical costs of users of the originators., Competing Interests: Yoon-Kyoung Sung has received research grants from Bristol-Myers Squibb, Eisai, Pfizer, and JW Pharmaceutical. Soo-Kyung Cho, Sun-Young Jung, Hyoungyoung Kim, Yeo-Jin Song, and Kyungeun Lee have nothing to declare., (© 2021 The Korean Academy of Medical Sciences.)

Background: Patients with rheumatoid arthritis (RA) undergoing targeted therapy have a higher risk of developing tuberculosis (TB). This requires diagnosis and treatment of latent tuberculosis infection (LTBI). We aimed to evaluate whether diagnosis and treatment of LTBI in RA are effective in Korea, and to estimate the risk of TB development by calculating the incidence rate of active TB among RA patients receiving targeted therapy., Methods: We analyzed data from two prospective cohort studies of RA patients who received biologic disease-modifying antirheumatic drugs (bDMARDs) or Janus kinase (JAK) inhibitor. We selected new starters of targeted therapy and classified them into three groups receiving tumor necrosis factor (TNF) inhibitor, non-TNF inhibitor, and JAK inhibitor, respectively. We then compared LTBI prevalence, treatments, and active TB incidence during first-line therapy in each group., Results: A total of 765 RA patients (574 TNF inhibitor users, 132 non-TNF inhibitor users, and 59 JAK inhibitor users) were included in this study. Observation periods were 1,255.2 person-years (PYs), 264.7 PYs, and 53.3 PYs, respectively. All 765 patients underwent LTBI screening, and the positivity rate was 26.5% (n = 203). Of the 203 LTBI-positive patients, 189 (93.1%) received treatment. Only one patient, who was in the TNF inhibitor group, and was negative for the interferon gamma release assay (IGRA), did not receive LTBI treatment and developed active TB during follow-up., Conclusion: Although the prevalence of LTBI in RA patients who started targeted therapy was slightly elevated, the Korean guidelines specifying LTBI screening and treatment were effective in preventing latent TB from becoming active., Competing Interests: DHY received research grants from Celltrion and HR, and is on the speakers bureau of Celltrion and Celltrion Healthcare. YKS received research grants from Bristol-Myers Squibb, Eisai, Pfizer, and JW Pharmaceutical. YJS, SKC, HK, HWK, EN, and SCB have no disclosures to declare. All authors declare no conflict of interest associated with this work., (© 2021 The Korean Academy of Medical Sciences.)

Background: To identify factors for starting biosimilar TNF inhibitors (TNFI) in patients with rheumatic diseases., Methods and Finding: Using a national claims database, we identified patients with rheumatoid arthritis (RA) or ankylosing spondylitis (AS) who had used TNFIs since they were approved in Korea in 2004. We assessed changes in the proportion of each form of TNFI used between 2004 and 2017. We then selected patients starting on TNFIs between 2013 and 2017 to identify factors for starting biosimilars. In RA (n = 4,216), biosimilars were more likely to be initiated in clinics [odds ratio (OR) 2.54] and in the metropolitan area (OR, 2.02), but were less likely to be initiated in general hospitals (OR 0.40) or orthopedics (OR 0.44). In AS (n = 2,338), biosimilars were common at the hospital level (OR 2.20) and tended to increase over the years (OR 1.16), but were initiated less in orthopedics (OR 0.07). In addition, RA patients were more likely to initiate biosimilars in combination with methotrexate (OR 1.37), but biosimilars were not initiated frequently by patients with higher comorbidity scores (OR 0.97) or receiving glucocorticoids (OR 0.67). The patient factors favoring biosimilar in AS use were not clear., Conclusions: In Korea, the proportion of biosimilar TNFIs has increased. Type of institution and physician specialty are more important than patient factors in affecting biosimilar use. In RA, biosimilar TNFIs tend to be initiated in combination with MTX, and are less likely to be initiated in patients taking glucocorticoids or in those with high comorbidities., Competing Interests: YKS has received research grants from Bristol-Myers Squibb, Eisai, Pfizer, and JW Pharmaceutical. HK, SC, SGI, YSL, SYJ, EJJ and SKC have nothing to declare. All authors declare no conflict of interest on this work. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Aim: To compare medication prescriptions for patients with knee osteoarthritis (KOA) in the real world in Korea and Japan., Methods: This retrospective and descriptive population-based study was conducted using claims data provided by Health Insurance Review and Assessment in Korea and JMDC Inc in Japan. We defined individuals as KOA patients if they had an International Classification of Diseases 10 (ICD10) code for gonarthrosis (M17) and were ≥50 years old in 2012. Korean and Japanese patients were matched for age and sex using frequency matching. Patients were observed for 1 year from the first month of the ICD10 code M17 in 2012. We described baseline characteristics including prevalence of comorbidities, and use of medication for KOA during the observational period., Results: The median age was 59 and the percentage of women was 61.4 in both countries (N = 1 133 138 in Korea, N = 10 498 in Japan). The prevalence of nonsteroidal anti-inflammatory drug (NSAID) usage in Japan (74.7%) was significantly higher than that in Korea (59.0%). Analgesics such as acetaminophen and symptomatic slow-acting drugs for OA (SYSADOA) were significantly more frequently used in Korea (25.8%) than in Japan (9.4%). Intra-articular injection (IAI) of corticosteroids or hyaluronic acid was performed more frequently in Japanese patients (57.3%) than Korean patients (30.5%)., Conclusions: Medication patterns for KOA in Korea and Japan are described for the first time. Use of NSAIDs and IAI were more common in Japan, while other pain killers and SYSADOA were more commonly prescribed in Korea., (© 2019 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

Background/aims: To evaluate the treatment patterns of knee osteoarthritis (OA) patients in South Korea., Methods: Using the Korean nationwide claims database, all knee OA patients in Korea during 2014 were identified by the knee OA diagnostic code (M17) or any OA diagnostic code (M15 to M19) in combination with a procedure for a knee X-ray. Patterns of medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids (CSs), analgesics, and symptomatic slow acting drugs for OA (SYSADOA) were analyzed. Prevalence and characteristics of knee OA patients who received a CS intra-articular injection (IAI) were also evaluated., Results: We identified 2,016,516 knee OA patients whose age (mean ± standard deviation) was 63.2 ± 10.8 years. The number of patients with at least one use of NSAIDs, analgesics, CS, and SYSADOA were 82.5%, 32.2%, 8.6%, and 43.4%, respectively. The use of herbal SYSADOAs was 29.7%. For regular users (medication possession ratios ≥ 50%), the use of NSAIDs was substantially decreased (48.8%), while the use of SYSADOA (37.3%) and CS (6.7%) were not significantly changed. The number of CS IAI users among knee OA patients was 0.18%; they were slightly older (64.4 ± 10.9 vs. 63.2 ± 10.8, p < 0.01) and more skewed towards females (75.7% vs. 71.5%, p < 0.01) than patients who had not received CS IAI., Conclusion: In Korea, the use of SYSADOA or CS in knee OA patients was relatively high. Further studies on the effectiveness and the safety of these treatment options for knee OA are needed.

Clinical research is the study of aspects of patient health or illness that are closely related to clinical practice. In the late 20th and early 21th century, outcomes for patients with rheumatoid arthritis (RA) improved dramatically due to breakthroughs in new drugs. Patient-reported outcome measures now play a significant role in the drug development process as study endpoints in clinical trials of new therapies, and this has led to increased interest in the patient's perspective, drug safety and treatment outcomes in clinical practice. In accordance with these needs, many prospective cohorts for RA patients and registries of biologic disease modifying anti-rheumatic drugs have been actively conducted in the United States and European and Asian countries. A gradual shift is taking place in the major outcomes of clinical research using these prospective cohorts and registries. This article will introduce representative registries for RA in each country set up in the early 2000s and will discuss future perspectives in clinical research on RA patients using such clinical registries.

Aim: To estimate incidence rate (IR) and risk factors for opportunistic infections (OI) in early rheumatoid arthritis (RA) patients., Methods: Retrospective cohorts were identified in the Korean National Claims Database. Incident RA cases were recruited in 2010 (n = 14 081). Follow up was ended at the time of development of new OI or at the date of last visit within 12 months of diagnosis. The IR and standardized incidence ratio (SIR) of OI in early and overall RA (n = 226 838) over a year were calculated. A multivariable regression model was used to identify risk factors for OI in early RA., Results: The IR of OI in early and overall RA were 3.81/100 and 3.67/100 person-years, respectively. The SIR for OI in early RA was 1.14 (95% CI, 1.05-1.23). Herpes zoster (SIR = 1.12, 95% CI, 1.03-1.22) and candidiasis (SIR = 2.40, 95% CI, 1.55-3.54) were common in early RA. Age (50 < age ≤ 60 [OR 1.74, 95% CI, 1.30-2.33], 60 < age ≤ 70 [OR 1.85, 95% CI, 1.36-2.52], age > 70 [OR 1.89, 95% CI, 1.34-2.68]), female sex (OR 1.40, 95% CI, 1.12-1.74), comorbidities (one comorbidity [OR 1.53, 95% CI, 1.24-1.89], ≥ two comorbidities [OR 1.84, 95% CI, 1.47-2.29]), and corticosteroid use of 5 mg/d or more (OR 1.38, 95% CI, 1.13-1.69) were significantly associated with increased risk of OI in early RA., Conclusion: Opportunistic infections, especially for herpes zoster and candidiasis, tend to occur more often in early RA than in overall RA. Age, female sex, comorbidities and corticosteroid use are related to increased OI in early RA patients., (© 2019 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

Aim: Despite high clinical disease activity, some patients with active rheumatoid arthritis (RA) have normal acute phase reactant (APR) values. This study aimed to determine the clinical outcomes of active RA patients with normal APR values., Method: Of 5376 patients with RA enrolled in the Korean observational study network for arthritis (KORONA) registry, 400 patients with disease duration of <2 years who had Clinical Disease Activity Index (CDAI) score of >2.8 at baseline, biologic-naïve, and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) drawn at both baseline and 2-year follow-up visits were identified. Patients were grouped according to baseline APR levels: normal APRs, one APR elevated, and both APRs elevated., Results: Baseline tender and swollen joint counts, mean CDAI and Health Assessment Questionnaire-Disability Index (HAQ-DI) scores were significantly lower in the normal APRs group compared with APR-elevated groups (P < 0.0001). At 2-year follow-up, mean CDAI scores, HAQ-DI, and percentage of the patient achieving remission were not significantly different between the normal APRs group compared with the APR-elevated groups regardless of the baseline disease activity. However, in patients with baseline CDAI moderate to high disease activity, the normal APRs group less frequently required initiation of the biologic disease-modifying anti-rheumatic drugs compared with the APR-elevated groups (P = 0.044)., Conclusion: Active RA patients with normal APR values have milder disease presentation, but similar clinical outcomes to those with elevated APRs., (© 2019 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

Aim: To determine characteristics of rheumatoid arthritis (RA) patients in Korea using disease-modifying anti-rheumatic drugs (DMARDs) for at least 6 months, and to identify factors associated with poor health-related outcomes., Method: A total of 2000 RA patients aged > 20 years, treated with DMARDs for at least 6 months, and signed informed consent, were enrolled in this non-interventional, multicenter, cross-sectional observational study from December 2012 to June 2013. Health-related quality of life (HRQoL) was measured using EuroQuol 5D (EQ-5D) and functional disability was measured using the Korean Health Assessment Questionnaire (KHAQ). Univariate and multivariate linear regression analyses were used to determine the association between patient characteristics and patient-reported outcomes (PROs)., Results: Of all RA patients, 84% were female, patients with low Disease Activity Score of 28 joints erythrocyte sedimentation rate (DAS-28-ESR < 3.2) was 54%, while moderate (DAS-28-ESR 3.2-5.1) and high disease activity score (DAS-28-ESR > 5.1) were 38% and 7.6%, respectively. Mean EQ-5D index score and KHAQ score were 0.6 ± 0.28 and 0.7 ± 0.67, respectively. In multivariate analysis with both PROs, average HRQoL and functional disability score appeared to be worse in persons with older age compared to younger age (P < 0.001), and worse in females compared to males (P < 0.001). Compared to patients having lower DAS (< 3.2), those with moderate and highest DAS (3.2-5.1 and > 5.1) had worse outcome measures (P < 0.001)., Conclusion: In this study, higher DAS was one of the most influential factors for poor PROs among all other factors. Therefore, we could suggest appropriate treatment approaches according to DAS along with other significantly associated factors with PROs in the early stage of RA., (© 2016 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

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.

Objectives: To estimate the incidence of cardiovascular disease (CVD) in Asian patients with rheumatoid arthritis (RA) and to evaluate the impact of anti-rheumatic treatment on the development of CVD., Methods: A retrospective cohort of Asian patients with RA was established to identify the incidence rate (IR) of CVD in RA patients. The cohort was generated using the Korean National Healthcare claims database, which contained claims from Jan 2009 to Dec 2013. A total of 137,512 RA patients were identified; individuals with a history of CVD for 6 months or more before the index date were excluded. Nested case-control samples were drawn from the full study population with a case:control ratio of 1:4 (n = 7102 cases; n = 27,018 controls without CVD). A conditional multivariate regression model was used to evaluate the impact of anti-rheumatic treatment on the development of CVD in RA patients after matching for age, sex, RA index date, comorbidities, and drug use (e.g., antiplatelet agents and cholesterol-lowering agents)., Results: The IR for development of overall CVD in RA patients was 182.1 (95% CI: 178.4-185.9) per 10,000 person-years. In models adjusted for other CVD risk factors, disease-modifying anti-rheumatic drugs (DMARDs) (OR = 0.79) were protective against CVD, and biologic DMARDs were not significantly associated with CVD risk (OR = 0.85). Corticosteroids (OR = 1.26) and NSAIDs (nonselective NSAIDs: OR = 1.32, Cox-2 inhibitors: OR = 1.31) were risk factors for CVD in RA patients., Conclusions: The use of DMARDs is protective against CVD, while corticosteroids and NSAIDs increased the risk of CVD in RA patients., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Treatment with disease-modifying anti-rheumatic drugs (DMARDs) has raised concerns about the risk of malignancies in rheumatoid arthritis (RA) patients. However, the association between biologic DMARDs (bDMARDs) and malignancy in previous reports remains controversial. Therefore we aimed to estimate the incidence of malignancy in early RA patients and to evaluate the relative risk of malignancy with use of bDMARDs., Methods: A retrospective cohort of incident RA patients was established using the Korean National Claims Database. Among a total of 14,081 RA patients identified, 1684 patients with a history of malignancy were excluded. We calculated the incidence rate of overall and individual malignancies. The standardized incidence ratio (SIR) of malignancies in bDMARD users was compared to that in nonusers. Multivariable logistic regression analysis was used to evaluate the impact of bDMARDs on the development of malignancies in early RA patients., Results: A total of 12,397 early RA patients without a history of malignancy were enrolled. During 41,599 person-years (PY) of follow-up, 725 malignancies developed in 561 patients (174.3/10,000 PY) and 21 hematologic malignancies developed (5.0/10,000 PY). Patients treated with bDMARDs had a significantly lower incidence of overall malignancy compared to those not treated with bDMARDs (SIR 0.45 (95% CI 0.28-0.70)). However, this relationship was not significant with regard to hematologic malignancies (SIR 2.65 (95% CI 0.55-7.76)). On multivariable analysis, bDMARD use was a protective factor against the development of overall malignancy (odds ratio 0.42 (95% CI 0.25-0.73)). However, bDMARD use had no significant protective effect against the development of hematologic malignancies (odds ratio 1.69 (95% CI 0.38-7.59))., Conclusions: In early RA patients, bDMARD use decreases the overall risk of developing malignancies; however, it does not affect the risk of developing hematologic malignancies.

Objectives: To estimate the incidence of tuberculosis (TB) in rheumatoid arthritis (RA) patients treated with tumor necrotizing factor inhibitor (TNFI) and evaluate the safety of resuming biologic disease-modifying anti-rheumatic drugs (DMARDs) in patients who developed TB after anti-TNF treatment., Methods: We conducted an inception cohort study of RA patients in the Korean Healthcare Claims Database who started TNFI as the first biologic DMARD between January 2009 and December 2013. The incidence rate (IR) of TB was estimated among total TNFI starters and a nested case-control analysis was performed to compare the characteristics of patients who developed TB and those did not. Patients diagnosed with relapsed TB after resuming biologic DMARDs were identified and their features were described., Results: We included 4638 RA patients who started TNFI, contributing 8542 PYs of follow-up. The IR of TB in TNFI users was 1.10 (CI: 0.86-1.34) per 100 PYs. After the initial 6 months, the IR was highest at 1.56 (CI: 1.02-2.10) and decreased gradually over time. Among the 81 patients who developed TB, 30 patients (37.0%) resumed biologic DMARDs with a mean interval of 3.3 months after TB development. Two cases of TB were detected among 30 patients with an observational period of 45.7 PY., Conclusions: The IR of TB in RA patients who started TNFI was 1.10 per 100 PYs. This rate was highest during the first 6 months. Resumption of biologic DMARDs requires careful monitoring for TB relapse., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Objective: To compare the clinical effectiveness of two treatment strategies for active rheumatoid arthritis (RA) refractory to conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs): starting TNF inhibitors (TNFIs) or changing csDMARDs., Methods: We used two nationwide Korean RA registries for patient selection. TNFI users were selected from the BIOPSY, which is an inception cohort of RA patients starting biologic DMARDs. As a control group, we selected RA patients with moderate or high disease activity from the KORONA database whose treatment was changed to other csDMARDs. After comparing baseline characteristics between the two groups in either unmatched or propensity score matched cohorts, we compared potential differences in the 1-year remission rate as a primary outcome and changes in HAQ-DI and EQ-5D scores as secondary outcomes., Results: A total of 356 TNFI starters and 586 csDMARD changers were identified from each registry as unmatched cohorts, and 294 patients were included in the propensity score matched cohort. In the intention-to-treat analysis, TNFI starters had higher 1-year remission rates than csDMARD changers in both unmatched (19.1 vs. 18.4%, p < 0.01) and matched cohorts (19.7 vs. 15.0%, p < 0.01). In per protocol analysis, TNFI starters had much higher remission rates in unmatched (37.2 vs. 28.0%, p = 0.04) and matched cohorts (35.4 vs. 19.1%, p = 0.04). However, in matched cohorts, no significant differences were observed between two groups in HAQ-DI and EQ-5D scores., Conclusions: We compared the clinical effectiveness of the two treatment strategies for active RA refractory to csDMARDs. TNFI starters showed higher 1-year remission rates than csDMARD changers.

To compare the characteristics of rheumatoid arthritis (RA) patients receiving either biosimilar or originator infliximab and to identify the effectiveness and safety of biosimilar infliximab in RA patients in real-world practice. RA patients who started either biosimilar or originator infliximab were selected using the prospective biologic disease-modifying anti-rheumatic drugs (DMARDs) registry: BIOlogics Pharmacoepidemiologic StudY (BIOPSY). Baseline characteristics of the two groups were compared, and short-term treatment outcomes, including DAS28-ESR and HAQ-DI scores, were compared after initiation of biosimilar or originator infliximab. The drug retention rates of the two groups were also compared. A total of 100 RA patients, 55 biosimilar, and 45 originator infliximab users were included in this analysis. Baseline characteristics of age, disease duration, and previous or current medications were similar in the two groups. Baseline DAS28-ESR was higher in the originator infliximab group (6.3 ± 1.1 vs. 5.8 ± 1.1, p = 0.02). The early DAS28-ESR remission rates observed 7.9 ± 1.8 months after starting biosimilar and originator infliximab were 15.0 and 25.0%, respectively (p = 0.47). The change in HAQ-DI did not differ between the two groups (0.4 ± 0.7 vs. 0.4 ± 0.8, p = 0.94). Patients treated with biosimilar infliximab in clinical practice had lower disease activity at the start of treatment than those receiving originator infliximab. Biosimilar infliximab was well-tolerated, safe, and of similar clinical effectiveness to originator infliximab. Larger number of patient and longer follow-up data will be needed to confirm the effectiveness and safety of biosimilar infliximab in clinical practice.

Remission is a primary end point of in clinical practice and trials of treatments for rheumatoid arthritis (RA). The 2011 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) remission criteria were developed to provide a consensus definition of remission. This study aimed to assess the concordance between the new remission criteria and the physician's clinical judgment of remission and also to identify factors that affect the discordance between these two approaches. A total of 3,209 patients with RA were included from the KORean Observational Study Network for Arthritis (KORONA) database. The frequency of remission was evaluated based on each approach. The agreement between the results was estimated by Cohen's kappa (κ). Patients with remission according to the 2011 ACR/EULAR criteria (i.e. the Boolean criteria) and/or physician judgment (n = 855) were divided into three groups: concordant remission, the Boolean criteria only, and physician judgment only. Multinomial logistic regression analysis was used to identify factors responsible for the assignment of patients with remission to one of the discordant groups rather than the concordant group. The remission rates using the Boolean criteria and physician judgment were 10.5% and 19.9%, respectively. The agreement between two approaches for remission was low (κ = 0.226) and the concordant remission rate was only 5.5% (n = 177). Pain affected classification in both discordant groups, whereas fatigue was associated with remission only by physician clinical judgment. The Boolean criteria were more stringent than clinical judgment. Patient subjective symptoms such as pain and fatigue were associated with discordance between the two approaches., Competing Interests: The authors have no potential conflicts of interest to disclose.

Background: The concerns about the development of adverse events (AEs) in elderly RA patients as a result of age-related changes in drug metabolism and the presence of comorbid illnesses are emphasizing due to increasing prevalence of rheumatoid arthritis (RA) in old age. However, they tend to be inadequately represented in RA clinical trials because of the exclusion criteria that are commonly applied. The tolerability and safety of TNF inhibitors in elderly patients have not been also evaluated in clinical practice. This study aimed to evaluate the retention rate and safety of TNF inhibitors (TNFI) in elderly RA patients., Methods: Total 429 RA patients (838 person-years [PYs]) treated with TNFI from a retrospective biologic DMARDs registry. Patients were divided into an elderly (age ≥60 years) and a younger group (<60 years). The drug retention rates of both groups were compared using Kaplan-Meier curves. Potential predictors of TNFI discontinuation in the elderly were examined using Cox regression analysis. The incidence rate (IR) of serious adverse events (SAEs) in the elderly group was compared to that of the young group., Results: Of the patients, 24.9 % (n = 107, 212 PYs) were in the elderly group. Regarding the retention rates of TNFI in 3 years, there was no significant difference between the elderly and younger group (p = 0.33). The major cause of discontinuation in elderly patients was AE (34.3 %), whereas that was drug ineffectiveness (41.7 %) in younger patients. Age (HR 1.09, CI 1.02-1.16) was a predictor of discontinuation, while the presence of comorbidity (HR 0.37, CI 0.15-0.91) had a protective effect against drug discontinuation in the elderly. The IR of SAEs in the elderly (6.13/100 PYs) was higher than in the younger group (5.11/100 PYs)., Conclusions: The retention rate of TNFI in the elderly was comparable with that in younger patients. The major cause of discontinuation in the elderly patients was AEs, while it was drug ineffectiveness in younger patients. The IR of SAEs in the elderly was higher than in the younger patients.

To investigate changes in the risk for serious infections (SIs) over time in Japanese rheumatoid arthritis (RA) patients treated with tumor necrosis factor inhibitors (TNFIs). This prospective cohort study included Japanese RA patients who began treatment with a TNFI from 2005 to 2007 (2005 group, n = 716, 634.2 patient years [PY]) and from 2008 to 2011 (2008 group, n = 352, 270.1 PY) at the time or after their enrollment in the registry of Japanese RA patients on biologics for long-term safety (REAL) database. Patients were observed for 12 months or until discontinuation of their initial TNFI in the REAL database. Drug discontinuation reasons and retention rates were analyzed. Incidence rates of serious adverse events (SAEs) were calculated with 95 % confidence intervals (CIs). The Cox proportional hazard model was applied to estimate the risk for SIs. The retention rate in the 2008 group was significantly lower than the 2005 group (p < 0.001). Discontinuation rates due to lack of efficacy or good control for the 2008 group were significantly higher than the 2005 group (p < 0.001). The crude incidence rate ratios comparing the 2008 group with the 2005 group for SAEs were 0.93 (95 % CI 0.65-1.34) and for SIs were 0.50 (0.24-1.03). The 2008 group had significantly lower risk for SIs than the 2005 group after adjusting for covariates (hazard ratio: 0.43 [0.20-0.93]). These results indicate significant decrease of the risk for SIs with TNFI treatment over time; this may be explained by evidence-based risk management of RA patients given TNFIs.

Objective: To compare the incidence and risk factors of serious adverse events (SAEs) in rheumatoid arthritis (RA) patients treated with etanercept (ETN) or adalimumab (ADA) between Korean and Japanese registries., Methods: We recruited 416 RA patients [505.2 patient-years (PYs)] who started ETN or ADA from Korean registry and 537 RA patients (762.0 PY) from Japanese registry. The patient background, incidence rate (IR) of SAE in 2 years, and risk factors for SAEs were compared., Results: Korean patients were younger and used more nonbiologic DMARDs, higher doses of methotrexate, and lower doses of prednisolone (PSL). The IR of SAEs (/100 PY) was higher in the Japanese registry compared to the Korean [13.65 vs. 6.73]. In both registries, infection was the most frequently reported SAE. The only significant risk factor for SAEs in Korean registry was age by decade [1.45]. In Japanese registry, age by decade [1.54], previous use of nonbiologic DMARDs ≥ 4 [1.93], and concomitant use of oral PSL ≥ 5 mg/day [2.20] were identified as risk factors for SAEs., Conclusions: The IR of SAE in Japan, especially infection, was higher than that of Korea, which was attributed to the difference of demographic and clinical characteristics of RA patients and treatment profiles.

The aim of this study is to evaluate tumor necrosis factor (TNF) inhibitor persistence and the impact of comorbidity on treatment persistence in patients with rheumatoid arthritis (RA). In a Korean National Health Insurance claims database, patients with a diagnosis code of RA (M05 or M06) who started TNF inhibitor therapy between July 1, 2007 and June 30, 2008 were enrolled. The study cohort was followed until December 31, 2009. Persistence was examined using Kaplan-Meier survival analysis, and multivariate Cox proportional hazard models were developed to examine the potential impact of comorbidities on drug persistence. A total of 388 patients were enrolled in the study cohort. The mean persistence rate in the overall population was 61% at 18 months. Drug survival rates for adalimumab and etanercept at 6 months were 82 and 85%, respectively, and 73 and 78%, respectively, at 12 months. Charlson comorbidity index (CCI) scores and comorbidities such as diabetes, chronic pulmonary disease, mild liver disease, and depression at initiation were not related with drug persistence, while peptic ulcer disease (PUD) lowered the risk of discontinuation of TNF inhibitors (HR 0.73, 95% CI 0.55-0.97). Old age (HR 1.59, 95% CI 1.09-2.33) and prescription of inhibitors by an internist (HR 1.59, 95% CI 1.02-2.48) were associated with discontinuation of TNF inhibitors. The persistence of TNF inhibitors was 61% at 18 months. CCI score and other comorbidities were not related with early discontinuation of TNF inhibitors, while PUD was an independent contributing factor to TNF inhibitor persistence.

TNF inhibitors are being used in a rapidly expanding number of rheumatoid arthritis (RA) patients due to their effectiveness and acceptable safety profiles. To date, concerns regarding the adverse effects of TNF inhibitors have focused on infections, hematologic malignancies, and demyelinating disorders. Recently, the development of autoantibodies and other autoimmunity has been increasingly reported. Here, we describe a 36-year-old RA patient in whom organizing pneumonia and systemic lupus erythematosus were detected during etanercept treatment.

Rheumatoid arthritis (RA) patients with chronic kidney failure are intolerant to most disease-modifying antirheumatic drugs (DMARDs) and NSAIDs due to their potential toxicities. Although the tumor necrosis factor (TNF) inhibitors have emerged as a highly effective treatment for RA, their safety and efficacy in RA patients with chronic kidney failure have not been well reported. We retrospectively evaluated the safety and efficacy of etanercept treatment in RA patients with chronic kidney failure. We describe three RA patients with chronic kidney failure who had been treated with DMARDs, steroids and NSAIDs, but were discontinued from these classical agents due to several side effects and nephrotoxicity. The patients were treated with 25 mg of etanercept once or twice a week. We evaluated disease activity and used decreasing renal function and increasing number of infections to monitor safety. All three patients improved after starting etanercept treatment and their steroid requirements were decreased. Linear relationships between Modification of Diet in Renal Disease study equation (MDRD) glomerular filtration rate (GFR) and time were observed. Thus, in all patients, the changes in GFR did not represent superimposed acute drug toxicity, but rather chronic progressive renal failure. These cases show that etanercept may be a safe and effective treatment option for RA patients with chronic kidney failure.

Background: The concerns about the development of adverse events (AEs) in elderly RA patients as a result of age-related changes in drug metabolism and the presence of comorbid illnesses are emphasizing due to increasing prevalence of rheumatoid arthritis (RA) in old age. However, they tend to be inadequately represented in RA clinical trials because of the exclusion criteria that are commonly applied. The tolerability and safety of TNF inhibitors in elderly patients have not been also evaluated in clinical practice. This study aimed to evaluate the retention rate and safety of TNF inhibitors (TNFI) in elderly RA patients.Methods: Total 429 RA patients (838 person-years [PYs]) treated with TNFI from a retrospective biologic DMARDs registry. Patients were divided into an elderly (age ≥60 years) and a younger group (<60 years). The drug retention rates of both groups were compared using Kaplan-Meier curves. Potential predictors of TNFI discontinuation in the elderly were examined using Cox regression analysis. The incidence rate (IR) of serious adverse events (SAEs) in the elderly group was compared to that of the young group.Results: Of the patients, 24.9 % (n = 107, 212 PYs) were in the elderly group. Regarding the retention rates of TNFI in 3 years, there was no significant difference between the elderly and younger group (p = 0.33). The major cause of discontinuation in elderly patients was AE (34.3 %), whereas that was drug ineffectiveness (41.7 %) in younger patients. Age (HR 1.09, CI 1.02-1.16) was a predictor of discontinuation, while the presence of comorbidity (HR 0.37, CI 0.15-0.91) had a protective effect against drug discontinuation in the elderly. The IR of SAEs in the elderly (6.13/100 PYs) was higher than in the younger group (5.11/100 PYs).Conclusions: The retention rate of TNFI in the elderly was comparable with that in younger patients. The major cause of discontinuation in the elderly patients was AEs, while it was drug ineffectiveness in younger patients. The IR of SAEs in the elderly was higher than in the younger patients. [ABSTRACT FROM AUTHOR]

The aim of this study was to estimate the mapping model for EuroQol-5D (EQ-5D) utility values using the health assessment questionnaire disability index (HAQ-DI), pain visual analog scale (VAS), and disease activity score in 28 joints (DAS28) in a large, nationwide cohort of rheumatoid arthritis (RA) patients in Korea. The KORean Observational study Network for Arthritis (KORONA) registry data on 3557 patients with RA were used. Data were randomly divided into a modeling set (80 % of the data) and a validation set (20 % of the data). The ordinary least squares (OLS), Tobit, and two-part model methods were employed to construct a model to map to the EQ-5D index. Using a combination of HAQ-DI, pain VAS, and DAS28, four model versions were examined. To evaluate the predictive accuracy of the models, the root-mean-square error (RMSE) and mean absolute error (MAE) were calculated using the validation dataset. A model that included HAQ-DI, pain VAS, and DAS28 produced the highest adjusted R as well as the lowest Akaike information criterion, RMSE, and MAE, regardless of the statistical methods used in modeling set. The mapping equation of the OLS method is given as EQ-5D = 0.95−0.21 × HAQ-DI−0.24 × pain VAS/100-0.01 × DAS28 (adjusted R = 57.6 %, RMSE = 0.1654 and MAE = 0.1222). Also in the validation set, the RMSE and MAE were shown to be the smallest. The model with HAQ-DI, pain VAS, and DAS28 showed the best performance, and this mapping model enabled the estimation of an EQ-5D value for RA patients in whom utility values have not been measured. [ABSTRACT FROM AUTHOR]

Several studies of rheumatoid arthritis (RA) incidence and prevalence indicate that occurrence of the disease varies significantly among different populations. We aimed to estimate the prevalence and incidence of RA in South Korea. We used Korean National Health Insurance (NHI) claims data to estimate the prevalence of RA in 2007-2009 and the incidence of RA in 2008. On the basis of our previous validation study, the presence of RA was defined by the diagnostic code for RA with biologic or non-biologic disease-modifying anti-rheumatic drugs in the same claim in each year. To estimate the incidence of RA, we identified cases of RA in 2008 and set the 12-month period prior to 2008 as a disease-free period. Among the incident case of 2008, only patients who continued treatment in 2009 were defined as true incident case of RA in 2008. The corresponding prevalence estimates were 0.26 % (95 % CI 0.25-0.27) in 2006, 0.27 % (95 % CI 0.26-0.28) in 2007, and 0.27 % (95 % CI 0.26-0.28) in 2008. The incidence of RA in 2008 was estimated at 42/100,000 (95 % CI 29.3-54.7) in the general population of South Korea. Data gathered nationwide through the NHI yielded estimates of RA prevalence and incidence in South Korea. This study is the first report of nationwide prevalence and incidence of South Korea and those are comparable to values for other countries in Asia. [ABSTRACT FROM AUTHOR]