Salivary Cotinine (PCS3)
Cotinine (a metabolite of nicotine) was assessed in saliva as a biochemical indicator of smoking rate. Because salivary cotinine concentration is not prone to self-report bias, it provides an objective measure of nicotine intake, and of passive smoke exposure among non-smokers.
Unstimulated saliva samples for measurement of cotinine were obtained at the physical exam (Visit 2). To collect the sample, participants placed a cotton roll into their mouths, chewed on it until it became saturated, and then placed it into the inner vial of a Salivette ® (Sarstedt, Rommelsdorft, Germany). Samples were coded and stored in coolers before being transferred, within 3 hours, to frozen storage at -70°C.
Saliva samples were tested for cotinine in duplicate using an enzyme immunoassay. The minimal concentration of cotinine that can be distinguished from zero is 0.05 ng/mL. The coefficient of variation for repeat assays is approximately 8% at a concentration of about 5 ng/mL, and approximately 5% for concentrations of about 102 ng/mL and above.
All cotinine assays were performed by Salimetrics, LLC (State College, PA). Additional details of the cotinine assay protocol can be found on the Salimetrics website.