title: Response to Letters to the Editors: 1. More details on the database used by the study should be provided. 2. Mediclaim Hospital Discharge System and income levels of cohort.
authors.affiliation: Duke-NUS Graduate Medical School Singapore, Singapore; Department of Rheumatology and Immunology, Singapore General Hospital, Singapore. Electronic address: katyccc@hotmail.com.
authors.forename: Y-Y
authors.initials: YY
authors.lastname: Leung
authors.affiliation: Epidemiology & Disease Control Division, Ministry of Health, Singapore.
authors.forename: L-W
authors.initials: LW
authors.lastname: Ang
authors.affiliation: Duke-NUS Graduate Medical School Singapore, Singapore.
authors.forename: J C
authors.initials: JC
authors.lastname: Allen
authors.affiliation: Duke-NUS Graduate Medical School Singapore, Singapore.
authors.forename: M
authors.initials: M
authors.lastname: Noviani
authors.affiliation: Division of Cancer Control and Population Sciences, University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA.
authors.forename: R
authors.initials: R
authors.lastname: Wang
authors.affiliation: Division of Cancer Control and Population Sciences, University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA; Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: J-M
authors.initials: JM
authors.lastname: Yuan
authors.affiliation: Duke-NUS Graduate Medical School Singapore, Singapore; Saw Swee Hock School of Public Health, National University of Singapore, Singapore. Electronic address: woonpuay.koh@duke-nus.edu.sg.
authors.forename: W-P
authors.initials: WP
authors.lastname: Koh
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D020370:Osteoarthritis, Knee / Q000209:etiology* / Q000601:surgery*; D012907:Smoking / Q000009:adverse effects*
keywords: MediClaim Database; Singapore; Socioeconomic status; Total knee replacement