[Measurement of the biochemical marker of smoking: urinary nicotine metabolites].

A novel, barbituric acid method of detecting urinary nicotine metabolites was evaluated for use as an objective test of smoking. Urine samples were collected from 289 male smokers and 167 male nonsmokers. The smokers recorded the number of cigarettes smoked on the previous day. This method correctly classified the subjects as smokers or nonsmokers. There was a significant positive correlation (r = 0.587, P less than 0.001) between the urinary nicotine metabolites/creatinine ratios and number of cigarettes smoked. This method can be performed very rapidly and reagent costs are very cheap. It is a good objective test of smoking and nicotine intake.