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Int J Environ Res Public Health. 2020 Feb 12;17(4). pii: E1157. doi: 10.3390/ijerph17041157.

Comparison of Liquid Chromatography Mass Spectrometry and Enzyme-Linked Immunosorbent Assay Methods to Measure Salivary Cotinine Levels in Ill Children.

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Division of Emergency Medicine, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA.
Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
School of Human Services, University of Cincinnati, Cincinnati, OH 45221, USA.
Department of Psychology, San Diego State University, San Diego, CA 92123, USA.


Objective: Cotinine is the preferred biomarker to validate levels of tobacco smoke exposure (TSE) in children. Compared to enzyme-linked immunosorbent assay methods (ELISA) for quantifying cotinine in saliva, the use of liquid chromatography tandem mass spectrometry (LC-MS/MS) has higher sensitivity and specificity to measure very low levels of TSE. We sought to compare LC-MS/MS and ELISA measures of cotinine in saliva samples from children overall and the associations of these measures with demographics and TSE patterns. Method: Participants were nonsmoking children (N = 218; age mean (SD) = 6.1 (5.1) years) presenting to a pediatric emergency department. Saliva samples were analyzed for cotinine using both LC-MS/MS and ELISA. Limit of quantitation (LOQ) for LC-MS/MS and ELISA was 0.1 ng/ml and 0.15 ng/ml, respectively. Results: Intraclass correlations (ICC) across methods = 0.884 and was consistent in sex and age subgroups. The geometric mean (GeoM) of LC-MS/MS = 4.1 (range: < LOQ - 382 ng/mL; 3% < LOQ) which was lower (p < 0.0001) than the ELISA GeoM = 5.7 (range: < LOQ - 364 ng/mL; 5% < LOQ). Similar associations of cotinine concentrations with age ( < -0.10, p < 0.0001), demographic characteristics (e.g., income), and number of cigarettes smoked by caregiver ( > 0.07, p < 0.0001) were found regardless of cotinine detection method; however, cotinine associations with sex and race/ethnicity were only found to be significant in models using LC-MS/MS-derived cotinine. Conclusions: Utilizing LC-MS/MS-based cotinine, associations of cotinine with sex and race/ethnicity of child were revealed that were not detectable using ELISA-based cotinine, demonstrating the benefits of utilizing the more sensitive LC-MS/MS assay for cotinine measurement when detecting low levels of TSE in children.


ELISA; cotinine; liquid chromatography; secondhand smoke exposure and children

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