cotinine level is associated with asthma severity in passive smoker children.

asthma environmental triggers play important roles in severity of disease. passive smoking could exacerbate asthma symptoms and enhance the decrease in lung function. cotinine levels could be a reflection of passive exposure to the cigarette both in adults and pediatrics. the aim of this study was to determine degree of association of asthma severity and cotinine level as a marker of passive smoking. in a cross-sectional study, 100 pediatric patients (under 10 years old) with asthma were enrolled, 50 of whom, had been exposed to passive smoking and 50 others included as controls. a complete clinical history, lab exam, and spirometry were performed. a sample of urine, serum and saliva was collected from all attendant patients and controls in the study after confirmation of diagnosis and determination of severity of asthma. the results revealed that age, sex, age of onset of asthma, family history and allergic history were not significantly different between two groups of patients. according to gina classification, percentage of patients with severe asthma was significantly higher in passive smoker group (p=0.001). cotinine was significantly higher in passive smoker group compared to control group in serum (p=001), saliva (p=0.001), and urine (p=0.0014). in passive smoker group, cotinine levels were significantly higher in serum (p=0.001), urine (p=0.007), and saliva (p=0.01) of patients with severe asthma than moderate and mild asthma. serum cotinine (or: 1.81, 95% ci: 1.35-2.32, p=0.024), urine cotinine (or: 3.56,95% ci = 1.29-5.53, p=0.01) and saliva cotinine (or: 1.66, 95% ci: 1.23-1.98, p=0.031) were also significantly associated with higher risk of severe asthma. cotinine levels were higher in passive smokers compared to non-passive smokers. besides, cotinine was a predictive risk factor for severe asthma.