title: Evaluation of Serum Cotinine Cut-Off to Distinguish Smokers From Nonsmokers in the Korean Population.
abstract: BACKGROUND
  Cotinine has been widely used as an objective marker to identify current smokers. We conducted this study to address the absence of Korean studies investigating the efficacy of immunoassays and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the detection of serum cotinine and to determine the optimal serum cotinine cut-off level for differentiating current smokers from nonsmokers.
  
  
  METHODS
  Serum specimens were obtained from 120 subjects. They were randomly chosen to represent a broad distribution of urine cotinine levels based on a retrospective review of questionnaires and results of urine cotinine levels. We determined serum cotinine levels using the IMMULITE 2000 XPi Immunoassay System (Siemens Healthcare Diagnostics Inc., USA) and LC-MS/MS (API-4000, Applied Biosystems, USA). Correlation was analyzed between IMMULITE serum cotinine, urine cotinine, and LC-MS/MS serum cotinine levels. ROC curve was analyzed to identify the optimal IMMULITE serum cotinine cut-off level for differentiating current smokers from nonsmokers.
  
  
  RESULTS
  IMMULITE serum cotinine levels correlated with both urine cotinine and LC-MS/MS serum cotinine levels, with correlation coefficients of 0.958 and 0.986, respectively. The optimal serum cotinine cut-off level for distinguishing current smokers from nonsmokers was 13.2 ng/mL (95.7% sensitivity, 94.1% specificity) using IMMULITE.
  
  
  CONCLUSIONS
  This is the first study to investigate the use of LC-MS/MS for the measurement of serum cotinine and to determine the optimal serum cotinine cut-off level for the IMMULITE immunoassay. Our results could provide guidelines for differentiating current smokers from nonsmokers in the Korean population.
authors.affiliation: Department of Laboratory Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Kiwoong
authors.initials: K
authors.lastname: Ko
authors.affiliation: Department of Laboratory Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea. mjkkmd@gmail.com.
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Kwon
authors.affiliation: Institute of Metabolism, Green Cross Laboratories, Yongin, Korea.
authors.forename: Song Hyun
authors.initials: SH
authors.lastname: Yang
authors.affiliation: Institute of Metabolism, Green Cross Laboratories, Yongin, Korea.
authors.forename: Chul Jin
authors.initials: CJ
authors.lastname: Moon
authors.affiliation: Institute of Metabolism, Green Cross Laboratories, Yongin, Korea.
authors.forename: Eun Hee
authors.initials: EH
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea. drwhy@hanmail.net.
authors.forename: Hee Yeon
authors.initials: HY
authors.lastname: Woo
authors.affiliation: Department of Laboratory Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Hyosoon
authors.initials: H
authors.lastname: Park
mesh_terms: D000328:Adult; D019540:Area Under Curve; D044466:Asian People; D002851:Chromatography, High Pressure Liquid; D003367:Cotinine / Q000097:blood* / Q000652:urine; D005260:Female; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D056910:Republic of Korea; D012189:Retrospective Studies; D012907:Smoking; D011795:Surveys and Questionnaires; D053719:Tandem Mass Spectrometry
chemical_list: D003367:Cotinine
keywords: Cotinine; Cut-off; Korean; LC-MS/MS; Serum