Background: Biomarkers of tobacco exposure haveacentral role in studies of tobacco use and nicotine intake. The most significant exposure markers are nicotine itself and its metabolites in urine. Therefore, it is important to evaluate the performance of laboratories conducting these biomarker measurements. Methods: This report presents the results from a method performance study involving 11 laboratories from 6 countries that are currently active in this area. Each laboratory assayed blind replicates of seven human urine pools at various concentrations on three separate days. The samples included five pools blended from smoker and nonsmoker urine sources, and two additional blank urine samples fortified with pure nicotine, cotinine, and hydroxycotinine standards. All laboratories used their own methods, and all were based on some form of liquid chromatography/tandem mass spectrometry. Results: Overall, good agreement was found among the laboratories in this study. Intralaboratory precision was good, and in the fortified pools, the mean bias observed was < + 3.5% for nicotine, approximately 1.2% for hydroxycotinine, and less than 1% for cotinine (1 outlier excluded in each case). Both indirect and direct methods for analyzing the glucuronides gave comparable results. Conclusions: This evaluation indicates that the experienced laboratories participating in this study can produce reliable and comparable human urinary nicotine metabolic profiles in samples from people with significant recent exposure to nicotine. Impact: This work supports the reliability and agreement of an international group of established laboratories measuring nicotine and its metabolites in urine in support of nicotine exposure studies.
Bibliographical noteFunding Information:
Research reported in this publication was supported by the U.S. Centers for Disease Control and Prevention (L. Wang, J.T. Bernert, J. Feng, E. McGahee, S.P. Caudill, B.C. Blount, and J.L. Pirkle) and by grant number 1P50CA180890 from the U.S. National Cancer Institute and the U.S. Food and Drug Administration Center for Tobacco Products (N.L. Benowitz and P. Jacob III). The content is solely the responsibility of the authors and does not necessarily represent the official views of the CDC, NIH, or FDA.