Association between creatinine-adjusted and unadjusted urine cotinine values in children and the mother's report of exposure to environmental tobacco smoke.

OBJECTIVE

To examine the association between parents' report of their child's secondhand smoke exposure and various adjustments of cotinine concentrations in random urine samples.

METHODS

Urine cotinine and creatinine were measured in 109 six to 11-year-old children from predominantly upper middle-class families. Cotinine values were considered as: (a) unadjusted, (b) as a cotinine/creatinine ratio, (c) as adjusted based on a regression relationship between cotinine and creatinine, and (d) and (e) as a cotinine/creatinine ratio adjusted for age and sex.

RESULTS

Little overlap in cotinine values occurred between exposed and nonexposed children, and a dose-response relationship was noted between the parental report and the urine cotinine values (r = 0.67). A modest improvement occurred in the correlation when the cotinine/creatinine ratio was considered. Considering exposure to cigarette smoke outside the home as well as in the household only improved the correlation when the former exposure was heavy. A high degree of concordance exists between the parents' report of exposure and the child's urine cotinine.

CONCLUSIONS

The value of adjusting this biochemical parameter by various means may be a function of the particular sample being investigated, suggesting no one method is universally appropriate.