We found that the majority of parents wanted their child tested for tobacco-smoke exposure in the context of their pediatric visit. Somewhat surprisingly, a similar majority of parents who smoke wanted their child tested. Majority support for testing persisted across all sociodemographic, geographic, and practitioner categories surveyed. Parents with lower education, women, nonwhites, and those who lived in homes where smoking was allowed were all more likely to want their child tested for tobacco-smoke exposure. Favorable parental attitudes toward testing in some of these groups may be reflective of greater tobacco exposure of their children, making the test more likely to show a positive exposure result.
Strong majorities of parents who smoke and those who do not would accept testing if it were an add-on to an existing blood test. This additional information about blood-test acceptability could be important in deciding how to operationalize a test for tobacco-smoke exposure in the context of busy office practices.
The study results are more generalizable because of the nationally representative sample; however, detailed racial and ethnic comparisons were limited by small cell size. Understanding more about how testing children for tobacco smoke might be perceived by the respondents, beyond simple approval of the test, was not possible in this survey.
Currently, there is not 1 “ideal” test for tobacco-smoke exposure, so the current gold standard is probably a combination of survey measures and cotinine testing.16,17
Having a biological test may decrease the underreporting of tobacco use and exposure that normally occurs as a result of the social stigma associated with tobacco use.18–20
Getting test results of exposure may help put some parents at ease, knowing that their children are unexposed. However, more likely, it will confirm a suspicion of exposure. In this case, the results might help nonsmokers advocate for safer environments for themselves and their children at home, in the car, at day care, or in other places children spend time. Parental smokers themselves may be genuinely curious to know whether their mitigation efforts are working. Some smokers may believe it is safe to smoke inside when children are not present. However, recent studies indicate that house dust and surfaces become contaminated when cigarettes are smoked indoors.9
When faced with data showing that their children still are exposed, they may enforce stricter smoking bans, have increased motivation to quit smoking, or be more likely to use nicotine-replacement therapy.
At present, the marker that is best suited to detect an individual's tobacco use and exposure is cotinine, a primary metabolite of nicotine and thus specific for tobacco smoke.21
Cotinine can be measured in a variety of tissues and body fluids, including blood, saliva, urine, hair, nails, and teeth. The levels of cotinine in each of these fluids and tissues vary on the basis of the type of sample, the intensity of the exposure, the time elapsed since exposure, and the metabolism of the individual. At present, there are no commercially available assays for cotinine assessment other than the urine dipsticks that are designed for qualitative assessment of active smoking.22
Low-level cotinine assessment is currently only accomplished by specific research laboratories and thus is not reimbursable by insurance. In addition, these research assays all require a substantial amount of processing, thus results are not available for immediate feedback and more often take weeks for reporting. Regarding the type of sample best suited for use in children, serum seems to be the most reliable.10
Given that many young children are screened for lead exposure and iron deficiency by a blood test, an additional aliquot of serum for cotinine assay at these testing points would not alter current pediatric practice.
Saliva collection may be problematic because of the need for the child to hold a swab in his or her mouth for a sufficient time to collect an adequate sample. Collection of hair samples, indicating a longer period of tobacco-smoke exposure, also can be challenging because they need to be cut closely to the scalp, and the direction of hair growth must be indicated on the sample. Collection of a sufficient quantity of hair may be objectionable for parents. Similarly, collection of a sufficient quantity of nail clippings is difficult in a young child.
Urine is arguably one of the easiest samples to obtain, either by a toilet-trained child voiding into a cup or a diapered child voiding onto cotton batting from which the urine can be collected. The hydration status of the child may alter the levels of cotinine substantially, however, requiring a correction for urinary creatinine,6
which can vary substantially with the age of the child. In addition, there is a great deal of variability between subjects and within subjects for urine, saliva, and serum cotinine, such that a similar cotinine level from 2 different subjects may represent differing levels of tobacco-smoke exposure. In addition, within an individual child, a single urine cotinine is only accurate for very recent (2–3 days) exposure, with a high level of variability such that an individual measure is very unlikely to represent an average tobacco-smoke exposure over time.23
As such, single measures of urinary cotinine cannot reliably ascertain changes in exposure to tobacco smoke.
Single measures of cotinine can be used qualitatively, however, to demonstrate exposure to tobacco smoke. In several studies24–27
, of variable success, that have sought to use cotinine feedback to intervene with parents about their own smoking as it impacts on their child's cotinine levels, none were able to provide rapid feedback of tobacco-smoke exposure levels because of the testing procedure, thus personal correlation by the parent or caregiver of times of exposure would have been difficult.24–27
These studies attempted to use cotinine as a biomarker for tobacco-smoke exposure reduction and did not focus on the delivery of state-of-the-art tobacco dependence treatment for parents. In addition, the overall source of exposure to tobacco smoke is likely more complex than has often been considered, and a cotinine level is likely to be a blend of actual smoke exposure plus that of nicotine contamination, or third-hand smoke. Components of tobacco smoke, including nicotine, can be absorbed into surfaces such as furniture, walls, carpets, and clothing or deposit as house dust and then be reemitted as volatile toxic compounds over a period of days to months.9,28
Use of a single cotinine measure as a marker of exposure to home tobacco smoke is likely to be confounded by this tobacco-smoke contamination and its persistence. Therefore, future interventions that include biofeedback of child exposure may need to focus on using exposure as a teachable moment for delivery of cessation medications and quitline enrollment coupled with longer-term retesting for child exposure.