Limits...
Evaluation of Serum Cotinine Cut-Off to Distinguish Smokers From Nonsmokers in the Korean Population

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Selectivity of serum cotinine using LC-MS/MS (A) Noise peaks (B) Front ghost peak (C) Cotinine (D) Internal standard (IS). No noticeable differences are observed in the chromatograms. Cotinine and the IS are separated from the noise peaks, and IS is sufficiently separated from the front ghost peak.Abbreviation: cps, counts per second; LC-MS/MS, liquid chromatography-tandem mass spectrometry.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4940485&req=5

Figure 1: Selectivity of serum cotinine using LC-MS/MS (A) Noise peaks (B) Front ghost peak (C) Cotinine (D) Internal standard (IS). No noticeable differences are observed in the chromatograms. Cotinine and the IS are separated from the noise peaks, and IS is sufficiently separated from the front ghost peak.Abbreviation: cps, counts per second; LC-MS/MS, liquid chromatography-tandem mass spectrometry.

Mentions: We evaluated serum cotinine measurements using LC-MS/MS, which included selectivity, accuracy, precision, and linearity. Fig. 1 shows the selectivity of this method. No noticeable interferences were observed in the chromatograms. Cotinine and IS were separated from the noise peaks, and IS was sufficiently separated from the front ghost peak. The intra-assay and inter-assay precision and accuracy were determined by using blank serum samples spiked with aliquots of cotinine solutions at four concentrations. Five samples of each concentration were prepared and the solutions were measured on the same day as that of the intra-assay. Inter-assay reliability was determined by measuring the calibration curve on three different days. The precision and accuracy are shown in Table 2. The quantitation limit of cotinine was 1 ng/mL. The standard curve was linear over the concentration range 1 to 200 ng/mL (r2 >0.99, with r as the regression constant).


Evaluation of Serum Cotinine Cut-Off to Distinguish Smokers From Nonsmokers in the Korean Population
Selectivity of serum cotinine using LC-MS/MS (A) Noise peaks (B) Front ghost peak (C) Cotinine (D) Internal standard (IS). No noticeable differences are observed in the chromatograms. Cotinine and the IS are separated from the noise peaks, and IS is sufficiently separated from the front ghost peak.Abbreviation: cps, counts per second; LC-MS/MS, liquid chromatography-tandem mass spectrometry.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940485&req=5

Figure 1: Selectivity of serum cotinine using LC-MS/MS (A) Noise peaks (B) Front ghost peak (C) Cotinine (D) Internal standard (IS). No noticeable differences are observed in the chromatograms. Cotinine and the IS are separated from the noise peaks, and IS is sufficiently separated from the front ghost peak.Abbreviation: cps, counts per second; LC-MS/MS, liquid chromatography-tandem mass spectrometry.
Mentions: We evaluated serum cotinine measurements using LC-MS/MS, which included selectivity, accuracy, precision, and linearity. Fig. 1 shows the selectivity of this method. No noticeable interferences were observed in the chromatograms. Cotinine and IS were separated from the noise peaks, and IS was sufficiently separated from the front ghost peak. The intra-assay and inter-assay precision and accuracy were determined by using blank serum samples spiked with aliquots of cotinine solutions at four concentrations. Five samples of each concentration were prepared and the solutions were measured on the same day as that of the intra-assay. Inter-assay reliability was determined by measuring the calibration curve on three different days. The precision and accuracy are shown in Table 2. The quantitation limit of cotinine was 1 ng/mL. The standard curve was linear over the concentration range 1 to 200 ng/mL (r2 >0.99, with r as the regression constant).

View Article: PubMed Central - PubMed

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.

No MeSH data available.