Relationship Between Urinary Cysteinyl Leukotriene E₄ Levels and Clinical Response to Antileukotriene Treatment in Patients with Asthma

The aim of this study was to investigate and identify the relationship between urinary cysteinyl leukotriene E₄ levels and clinical response to antileukotriene treatment in patients with asthma. Forty-eight patients with stable mild to moderate asthma were treated with montelukast in a four-week trail. Asthmatic symptom score, β₂-agonist usage, percentage of eosinophil, total serum IgE concentration, forced expiratory volume in the first second (FEV₁), peak expiratory flow rate (PEFR), and urinary leukotriene E₄ (uLTE₄) were measured before and after treatment. Clinical response was assessed by the improvement of asthma symptom scores, β₂-agonist usage, and FEV₁. Responders were defined as patients who had to fit the following three criteria: a reduction of more than 20% in mean symptom score; a reduction of more than 20% in β₂-agonist usage, and a mean improvement of FEV₁ of more than 10% from baseline value. Others were classified as nonresponders. Logistic analysis was used to access the various clinical factors correlated with the clinical response. There were 25 responders and 23 nonresponders. The mean uLTE₄ level from the responders was higher than that from the nonresponders (224.5 ± 34.4 vs. 175.3 ± 37.1 pg/mg creatinine, p < 0.05). There was a significant correlation between the clinical response and the uLTE₄ level but not demographic features, percentage of eosinophils, serum IgE concentration, or spirometry (p > 0.05). Subjects with a uLTE₄ level of ≥ 200 pg/mg creatinine were 3.5 times more likely to respond to montelukast than those with less than 200 pg/mg creatinine (95% confidence interval [CI] = 1.7–15.8). The uLTE₄ level is closely correlated with antileukotriene treatment. uLTE₄ is a good biomarker for selecting this drug to treat asthma.