Passive smoking amongst asthmatic children: questionnaire or objective assessment?

An increasing number of studies have implicated passive smoking as a definite threat to non-smokers' health. Self-reports of smoking status may not always be reliable, particularly in situations where the smoker feels under pressure to give up smoking. In this study questionnaire and salivary cotinine, an objective measure of nicotine exposure, were studied in asthmatic and age-matched control children. We have consequently developed a sensitive assay for cotinine using high performance liquid chromatography (HPLC) to quantitate environmental tobacco smoke (ETS) exposure in a group of 5- to 7-year-old asthmatic and control children. We chose to use mixed unstimulated saliva collected by absorption into dental rolls in the mouth for 5 min. Our modified extraction procedure was highly reproducible with a >90% retrieval rate of cotinine from spiked saliva. The parents were asked to fill in a questionnaire on atmospheric pollutants to obtain an estimate of declared ETS exposure in the home. Results showed that 31% of the asthmatic patients were exposed to ETS, according to the parents, but by HPLC 69% had been so exposed (n=19). From the control group the figures were 40% and 50% of patients, respectively. Therefore, an objective assessment is essential as ETS is more ubiquitous than is apparent from the questionnaire alone. Finally, in this small number of individuals our objective assessment demonstrates that ETS exposure is more prevalent in asthmatic children (69%) than age-matched controls (51%)