Assessment of smoking status based on cotinine levels in nasal lavage fluid

Precise estimation of direct exposure to tobacco smoke is a problem for epidemiologic studies due to human errors and inaccuracy in self report. Assessment of passive exposure to tobacco smoke is even more problematic [1,2]. While nicotine has a relatively short half-life of about 2 hours, cotinine, a principal metabolite of nicotine, has a half-life of approximately 20 hours, and is a specific and sensitive marker for determining exposure to tobacco [3-5]. Therefore, measurement of salivary, urinary or serum cotinine values have been used to validate self-reported smoking status [1,4], with saliva providing the most easily obtained source [6-8].Notably, the olfactory sensory neuroepithelium and nasal mucosa are directly exposed to tobacco smoke in both smokers and non-smokers who live with or work around smokers. Smoking has been shown to reduce olfactory sensitivity in a dose- and time-dependent manner [9-12], and passive smoke exposure has been implicated in reduced olfactory function as well [13]. Using nicotine nasal spray caused adverse effects of nasal irritation and burning and taste and smell complaints [14]. Moreover, both exposures to tobacco smoke and to lipopolysaccharide, an active component of cigarette smoke, trigger a dramatic increase in the degree of olfactory neuron apoptosis [15,16].The impact of smoking on the nasal mucosa has received considerably less study than its impact on lower respiratory tissue. Nonetheless, there is evidence for multiple deleterious effects, including increased nasal resistance, decreased mucociliary flow and mucosal sensitivity, and induces increase in DNA adduct and may cause nasal tumors due to numerous chemicals found [17,18]. Histopathological analysis of nasal mucosa obtained from rats exposed to tobacco smoke revealed a decrease in the extent of olfactory epithelium including loss of cilia and development of metaplasia [19].Tobacco smoke may exert direct effects on nasal epithelial health and olfactory neuronal