Sputum Eosinophil Apoptotic Rate Is Positively Correlated to Exhaled Nitric Oxide in Children

Rationale for Study: Exhaled nitric oxide (FENO), a potential biomarker for asthma, is positively correlated with eosinophilic airway inflammation. Eosinophil apoptotic rate (AR) may be increased by NO but the relationship between eosinophil AR and NO has not been studied in vivo. This study tested the hypothesis that eosinophil AR will be positively related to FENO. Methods: Children with and without asthma were recruited and participated in an assessment that included FENO measurement, skin prick reactivity, spirometry, and sputum induction. The absolute sputum eosinophil count and eosinophil AR were determined by morphology under light microscope after staining. Results: There were 31 children recruited, mean age 11 years, 21 were asthmatic and 19 were boys. The median FENO (range) was 15.6 parts per billion (3.1 - 102.6), 17 were atopic and the mean (SD)% FEV1 was 85 (10)%. Sputum eosinophil AR was determined in 19 children (16 asthmatics), mean (SD) value 0.49 (0.13). There were positive relationships between eosinophil AR and FENO (Spearman rho = 0.46, P = 0.046), eosinophil AR and % eosinophil count (Spearman rho = 0.45, P = 0.050) and also FENO and % eosinophil count (Spearman rho = 0.49, P = 0.024). Conclusion: There is a positive relationship between FENO and eosinophil AR. Nitric oxide may be involved in regulation of eosinophil AR in the airways. Pediatr Pulmonol 2008; 43:1130-1134. (C) 2008 Wiley-Liss, Inc.