How to Measure Secondhand Smoke Exposure in a Pediatric Clinic Setting FREE

There has been a recent focus to decrease environmental tobacco smoke (ETS) exposure among children,^1- 2 but an important obstacle to overcome is how to accurately measure ETS exposure. Standardized questionnaires are associated with a high frequency of underreporting.^3- 4 Cotinine, a biomarker for tobacco exposure, appears to be a more promising method to accurately detect ETS exposure,⁵ but testing is currently expensive and results are not immediately available. We conducted a study to evaluate the use of a urine dipstick to measure cotinine as an alternative to the current complex testing.

Patients between the ages of 5 and 15 years and their smoking or nonsmoking caregiver who attended a busy urban Pediatric Pulmonary Clinic during February and March of 2010 were invited to participate in the study. The protocol was approved by the University of South Florida institutional review board.

The caregiver completed a smoking behavior questionnaire and a random urine sample was collected from the child to measure cotinine levels using Nymox TobacAlert test strips (Nymox Pharmaceutical Corporation, Saint-Laurent, Quebec, Canada). A level of 0 (0-6 ng/mL) represents no smoke exposure, levels of 1 (6-30 ng/mL) and 2 (30-100 ng/mL) represent secondhand smoke exposure, and levels of 3 to 6 (>100 ng/mL) represent a smoker.

Descriptive statistics were used to summarize smoking behavior, and group comparisons between smoking households and nonsmoking households were tested by Fisher exact test or χ² test for the categorical data or by 2-sample t test for the continuous data.

Of the 47 patients eligible for the study, 35 were enrolled. The most common reason for not enrolling was that the child had already voided. Approximately 77% of the population was white and 23% were black, with 26% of Hispanic ethnicity. Medicaid was the primary insurance for 51% of the patients. There were no significant differences in the demographics of the smoke-exposed and non–smoke-exposed children. The mean (SD) age of participants was 9 (3) years, with 50% of the population being male. The Smoking Behavior Questionnaire results are summarized in the Table. Of 17 patients living with a smoker, the most common family member who smoked was the mother (70%). Urine cotinine levels did not vary based on whether the smoker was the mother or another member of the household. While 29% of children lived with more than 1 household smoker, their urine cotinine levels were not higher than those living with 1 smoker. With the exception of 1 child, who had a cotinine level of 2 ng/mL (range, 30-100 ng/mL), all cotinine levels were at level 1 (range, 6-30 ng/mL). Of 17 children living with a household smoker, 16 children had positive cotinine levels. The patient with a negative cotinine level lived in a home with an enforced smoking ban in their home and car. Of 18 patients living in a nonsmoking household, 3 patients had positive urine cotinine levels with an identifiable source of exposure (a carpool parent, a visiting uncle, and a school bathroom).

Urine cotinine test strips are a noninvasive, quick, and easy alternative to measuring urine cotinine in a busy clinic setting. Testing does not require any instrumentation or special training, and results are available in less than 15 minutes.

The test strip is a sensitive indicator of ETS exposure in both smoking and nonsmoking households; however, it is not an effective measure of small changes in urine cotinine levels. The cotinine test strips, in conjunction with a smoking behavior questionnaire, were successful in documenting the source of ETS exposure in our study. A larger clinical trial with measurements over serial visits is needed to support the findings of this trial.