Correlation between reversibility of airway obstruction and exhaled nitricoxide levels in children with stable bronchial asthma

Recent trials measuring exhaled nitric oxide (eNO) concentrations have sugg ested that it may be a useful measure of ongoing airway inflammation in pat ients with asthma. The purpose of this study was to examine the relationshi p between eNO levels and baseline as well as postbronchodilator spirometry, a measurement commonly used in the clinical setting to determine the sever ity of asthma and as a guide to therapeutic decisions. Forty-nine patients between the ages of 5-16 years with physician-diagnosed asthma who attended the pediatric pulmonary clinic for a routine asthma visit with spirometric evaluation were recruited for the study, eNO levels prior to spirometry we re obtained before and after receiving inhaled beta (2) agonist, eNO sample s were collected in impermeable bags (Tedlar(R)) and assayed within 24 hr b y chemiluminescence. Regression analysis was used to assess the relationshi ps between pre- and postbronchodilator eNO and spirometric variables. eNO w as also compared in patients receiving and not receiving inhaled corticoste roids (ICS), as well as those whose therapy had been increased after evalua tion by a pediatric pulmonologist or allergist. We found no significant difference between the levels of eNO before and aft er inhalation of beta (2) agonist (P = 0.60 paired t-test). Positive correl ation was found between eNO vs. percentage change in FEV1 (r = 0.35, P = 0. 01) and percentage change in FEF25-75% (r = 0.29, P = 0.04). A negative cor relation was found between prebronchodilator FEV, and eNO (r = -0.29, P = 0 .03). Patients on ICS had lower mean eNO levels (29.9 vs. 47.6 parts per bi llion (ppb), P = 0.053) than those not receiving ICS. Patients whose ICS th erapy was increased had higher mean eNO levels (47.2 vs. 26.9 ppb, P = 0.01 8) than those not having ICS therapy increased. We suggest that eNO levels could be a clinically useful measurement of asth ma severity and could be used as an adjunct to spirometry to determine appr opriate treatment plans. Longitudinal clinical trials are needed to determi ne if eNO can enhance therapeutic decisions for asthmatic children. (C) 200 0 Wiley-Liss, Inc.