1992 Volume 2 Issue 2 Pages 91-95
Usefulness of urinary cotinine (COT)/creatinine (Cr) ratio, a widely accept practical indicator of tobacco smoke uptake, was evaluated in 4 groups of healthy male volunteers (21 in total) with different cigarette doses of 0, 10, 20 and 30 cigarettes per day. 24-hour urine samples were collected on the 7th day of successive controlled smoking to determine urinary COT, thiocyanate (SCN) and Cr concentrations. Although urinary COT concentration exhibited close correlation (r=0.91, p<0.01) with cigarette dose, this correlation was weakened to r=0.82 (p<0.01) when it was standardized by urinary Cr concentration. Urinary SCN concentration was, in contrast, unrelated to cigarette dose (r=0.09), which however become correlated (r=0.71, p<0.05) after Cr standardization, in part due to the variation of urinary Cr concentration which was found inversely linked to cigarette dose (r= -0.47, p<0.05). Multiple regression analyses revealed that extent of urine volume-dependent decrease in urinary COT concentrationwas of several orders smaller in magnitude than that of urinary SCN or Cr concentrations as estimated on the basis of standardized partial regression coefficients. These results suggested that urinary COT/Cr ratio, compared to urinary COT concentration, tends to exaggerate the actual smoke uptake in the individuals with increased urine flow as well as in the smokers with smoking-associated decrease in urinary Cr concentration. J Epidemiol, 1992; 2 : 91-95.
