Usefulness of Urinary Cotinine Test to Distinguish Smokers from Nonsmokers

Background : Self-reports of smoking may not always be reliable. A number of biochemical markers have been used to validate claims of nonsmoking, among which the most widely used specific marker has been the nicotine metabolite cotinine. This study was conducted to evaluate the performance of the enzyme immunoassay (EIA) for urinary cotinine to determine smoking status. Methods : Questionnaires on smoking and urinary cotinine measures were studied in 287 persons. Urinary cotinine concentration was measured by the Cotinine Enzyme Immunoassay (Diagnostic Reagents, Inc., CA, USA) on the 502X Multiple Chemistry Unit (A&T Co., Tokyo, Japan). Results : Using cutoffs of 0 ng/mL, 20 ng/mL or 100 ng/mL for urinary cotinine measured by the EIA method, the sensitivities were 100%, 97.6%, and 94.4% respectively and the specificities were 97.5%, 98.8%, and 100% respectively. By retrograde telephone questionnaires, 3.8% of the subjects were confirmed as deceiving their smoking status. Active smokers of 10 cigarettes (1,052 ng/mL). Conclusions : Urinary cotinine measured by EIA is a rapid, lab-based test that can reliably determine smoking status. Considering the various purpose of the test, different cut-offs should be used.