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A Validated Method for Urinary Cotinine Quantification Used to Classify Active and Environmental Tobacco Smoke Exposure

2013; Bentham Science Publishers; Volume: 9; Issue: 3 Linguagem: Inglês

10.2174/1573411011309030014

1875-6727

Silvia Fustinoni, Laura Campo, Elisa Polledri, Rosa Mercadante, Laura Erspamer, Andrea Ranzi, Paolo Lauriola, Carlo Alberto Goldoni, Pier Alberto Bertazzi,

Smoking Behavior and Cessation

The aims of this research were to develop and validate a simple, sensitive method to determine un-conjugated urinary cotinine (COT-U) levels and to investigate its ability to discriminate active and environmental tobacco smoke (ETS) exposure. For this assay, urine was diluted with water, cotinine-d3 was added as an internal standard, and the sample was separated by a C18 column and analysed by triple quadrupole mass spectrometry. The quantification limit was 0.1 μg/L, range of linearity was 0.1–4000 μg/L, intra- and inter-run precision were <10%, and accuracy was within 13% of the theoretical value. Investigation of the matrix effect showed that the internal standard controlled sources of bias. The assay was applied to 168 adults who classified themselves as non-smokers with (9.5%) or without (67.9%) ETS exposure, active smokers (20.2%), and those who did not report smoking information (2.4%). Median COT-U levels were 1.3, 0.6, 687, and 57 μg/L, respectively. Based on a critical evaluation of self-classification and COT-U levels, we proposed a 30- μg/L cut-off value to identify active smoking. The ability of COT-U levels to distinguish ETS exposure was evaluated among non-smokers, but a wide overlap between groups with and without ETS exposure prevented the identification of a reliable cut-off value. A 2-μg/L COT-U cut-off value correctly identified 95.4% of self-classified non-ETS exposure and 33.3% of self-classified ETS exposure. This method reliably measured a wide range of COT-U levels. The 30-μg/L cutoff value appropriately classified active tobacco smoke exposure, but the classification of ETS exposure needs further research. Keywords: Active tobacco smoke, biomonitoring, environmental tobacco smoke, LC-MS/MS, urinary cotinine