Sensitivity and specificity of a reagent-impregnated test strip in identifying smokeless tobacco users

This study was designed to determine the sensitivity and specificity of a reagent-impregnated test strip in identifying habitual snuff users and tobacco chewers. Urine specimens were obtained from smokeless tobacco users and controls and blind tested on-site using a reagent-impregnated test strip. Samples also were sent to our university hospital lab for cotinine and nicotine analysis by gas chromatography (GC). The test strip results were compared with GC results and self-reported use of snuff and chewing tobacco. A total of 61 subjects enrolled in the study: 26 snuff users, 25 tobacco chewers, and 10 nonconsumers of nicotine. Using GC assessment of nicotine and cotinine (>or=200 ng/ml) as the standard, we found the sensitivity of the test strip to be 96% (25/26) for snuff users and 96% (24/25) for tobacco chewers. When compared with self-report, the sensitivity of the test strip was 92.3% (24/26) for snuff users and 84% (21/25) for tobacco chewers. The specificity for nonusers of nicotine was 100% (10/10) for both the self-report and GC conditions. These results suggest that a reagent-impregnated test strip is a rapid, valid, and user-friendly means of differentiating smokeless tobacco users from nonconsumers of tobacco. The intensity of the pink color on the test strip is proportional to the amount of nicotine or its metabolites present in urine and therefore offers a semiquantitative measure of nicotine consumption.