Validation of Self-Reported Smoking Status Using Saliva Cotinine: A Rapid Semiquantitative Dipstick Method

Abstract

This study evaluated the performance characteristics of a novel rapid method for verifying smoking status in individuals by measurement of cotinine, the primary metabolite of nicotine, in saliva samples using an immunochromatographic strip in a "dipstick" format compared with liquid chromatography/mass spectrometry (LC/MS). A prospective comparison was made of smoking status as determined by measurement of cotinine in urine by LC/MS (the gold standard) and in saliva using a semiquantitative dipstick assay that uses cotinine-specific monoclonal antibodies attached to gold particles and a series of avidity traps to measure cotinine levels (saliva NicAlert). One hundred seventy-two individuals from a family practice/general medical setting agreed to participate after informed consent and institutional review board approval. Saliva NicAlert tests were done by untrained operators who followed written directions. Comparison of smoking status as determined by urine cotinine measurement by LC/MS (50 ng/mL cutoff) with the saliva strip test results, averaged over the two operators, indicated that the saliva test strip results had a sensitivity of 99% and a specificity of 96%. Saliva NicAlert also identified four smokers who reported being nonsmokers but were confirmed to be smokers by LC/MS. The saliva NicAlert assay seems to be a valid, highly sensitive, and specific method for validating self-reported smoking status and may have clinical applications in selected medical settings.