Study concept and design: J.-K. Lee, Hahn, D.-W. Kim.
Acquisition, analysis, or interpretation of data: J.-K. Lee, Hahn, D.-W. Kim, Suh, Keam, T. M. Kim, S.-H. Lee, Heo.
Drafting of the manuscript: J.-K. Lee, Hahn, Heo.
Critical revision of the manuscript for important intellectual content: J.-K. Lee, Hahn, D.-W. Kim, Suh, Keam, T. M. Kim, S.-H. Lee.
Statistical analysis: J.-K. Lee, Hahn, Keam.
Obtained funding: Hahn, D.-W. Kim.
Study supervision: Hahn, D.-W. Kim, T. M. Kim, S.-H. Lee, Heo.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr D.-W. Kim reports having received grants from the Korean government and personal fees from Pfizer, Lilly, and Novartis. Dr S.-H. Lee reports having received personal fees from Pfizer, Novartis, Bayer, and GlaxoSmithKline. No other disclosures were reported.
Funding/Support: This work was supported in part by National Research Foundation of Korea (NRF) grants funded by the Korean government (2010-0009563, 2012-0000994).
Role of the Sponsor: The funding source had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.