Use of cotinine immunoassay test strips for preclassifying urine samples from smokers and nonsmokers prior to analysis by LC-MS-MS

Cotinine biomarker measurements involving both smokers and nonsmokers must accommodate a broad range of concentrations. Thus, we have routinely preclassified unknown samples as being either "high" or "low" by using an enzyme-linked immunoassay for cotinine prior to analysis by tandem mass spectrometry (MS). Although this method is effective, it is also time-consuming and complex; a simpler and faster approach would be useful. Consequently, a screening assay for urine cotinine using an immunochromatographic test strip (NicAlert™) followed by a computerized analysis of the data was examined as a possible alternative. The results indicate that this approach can provide useful classification efficiency when using our target cutoff value of approximately 20 ng/mL. In the analysis of 50 urine samples from nonsmokers with varying degrees of exposure to environmental tobacco smoke, the classification sensitivity and specificity were 88% and 92%, respectively, for cotinine measured by the test strips relative to total cotinine concentrations measured by atmospheric-pressure ionization tandem MS. However, the relatively high cost of the strips may be a limiting factor.