Urinary leukotriene E4 levels identify children with tobacco smoke exposure at risk for asthma exacerbation

Background: Children with asthma exposed to secondhand smoke (SHS) might be at higher risk for severe exacerbations, but biomarkers of susceptibility to SHS exposure have not been previously reported. Objectives: We sought to assess the usefulness of urinary leukotriene E-4 (uLTE(4)) levels in the prediction of increased risk of severe asthma exacerbations requiring emergency department (ED) or urgent care (UC) visits. Methods: Forty-four schoolchildren with moderate-to-severe asthma receiving inhaled corticosteroids were followed for 5 months with repeated measurements of uLTE(4) and monitoring of ED and UC visits. SHS exposure status was determined by using prestudy questionnaires and repeated measurements of urinary cotinine during the study. Results: Nine (45%) of 20 children with SHS exposure experienced a severe exacerbation requiring an ED or UC visit compared with 3 (12.5%) of 24 children without significant SHS exposure (relative risk, 3.6; 95% CI, 1.1-11.5; P = .02). The uLTE(4) level was a significant predictor of exacerbation risk in children exposed to SHS (area under the curve, 0.85; P = .003). Other predictors, such as nighttime symptom frequency, prebronchodilator and postbronchodilator lung function, and exhaled nitric oxide levels, were not related to exacerbations in this group. uLTE(4) levels at or greater than 106 pg/mg achieved 67% (6/9) sensitivity and 100% (11/11) specificity for predicting children with SHS exposure who required an ED or UC visit. Conclusions: Children exposed to SHS are at increased risk for severe asthma exacerbations, despite use of inhaled corticosteroids. uLTE(4) levels identify children exposed to SHS at high risk for asthma exacerbations. (J Allergy Clin Immunol 2011;128:323-7.)