Background: Anatomic studies of boys with attentiondeficit/hyperactivity disorder (ADHD) have detected decreased volumes in total and frontal brain, basal ganglia, and cerebellar vermis. We tested these findings in a sample of girls with ADHD.

Background-Exhaled nitric oxide (FeNO) is a biomarker of airway inflammation. In the nitric oxide (NO) synthesis pathway, nitric oxide synthases (encoded by NOS1, NOS2A and NOS3) and arginases (encoded by ARG1 and ARG2) compete for L-arginine. Although FeNO levels are higher in children with asthma/allergy, influence of these conditions on the relationships between variations in these genes and FeNO remains unknown. The aims of the study were to evaluate the role of genetic variations in nitric oxide synthases and arginases on FeNO in children and to assess the influence of asthma and respiratory allergy on these genetic associations.

Background: Determinants of exhaled nitric oxide (FeNO) need to be understood better to maximize the value of FeNO measurement in clinical practice and research. Our aim was to identify significant predictors of FeNO in an initial cross-sectional survey of southern California schoolchildren, part of a larger longitudinal study of asthma incidence.

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Field measurements of exhaled nitric oxide (FeNO) and ambient nitric oxide (NO) are useful to assess both respiratory health and short-term air pollution exposure. Online real-time measurement maximizes data quality and comparability with clinical studies, but offline delayed measurement may be more practical for large epidemiological studies. To facilitate cross-comparison in larger studies, we measured FeNO and concurrent ambient NO both online and offline in 362 children at 14 schools in 8 Southern California communities. Offline breath samples were collected in bags at 100 ml/s expiratory flow with deadspace discard; online FeNO was measured at 50 ml/s. Scrubbing of ambient NO from inhaled air appeared to be nearly 100% effective online, but 50-75% effective offline. Offline samples were stored at 2-81C and analyzed 2-26 h later at a central laboratory. Offline and online FeNO showed a nearly (but not completely) linear relationship (R 2 ¼ 0.90); unadjusted means (ranges) were 10 (4-94) and 15 (3-181) p.p.b., respectively. Ambient NO concentration range was 0-212 p.p.b. Offline FeNO was positively related to ambient NO (r ¼ 0.30, Po0.0001), unlike online FeNO (r ¼ 0.09, P ¼ 0.08), indicating that ambient NO artifactually influenced offline measurements. Offline FeNO differed between schools (Po0.001); online FeNO did not (P ¼ 0.26), suggesting artifacts related to offline bag storage and transport. Artifact effects were small in comparison with between-subject variance of FeNO. An empirical statistical model predicting individual online FeNO from offline FeNO, ambient NO, and lag time before offline analysis gave R 2 ¼ 0.94. Analyses of school or age differences yielded similar results from measured or model-predicted online FeNO. Conclusions: Either online or offline measurement of exhaled NO and concurrent ambient NO can be useful in field epidemiology. Influence of ambient NO on exhaled NO should be examined carefully, particularly for offline measurements.