Exhaled nitric oxide as a predictor of exercise-induced bronchoconstriction.
BACKGROUND
Exercise-induced bronchoconstriction (EIB) is present in 40 to 90% of patients with asthma. Exhaled NO (eNO) levels have been correlated with bronchial hyperresponsiveness to methacholine, and have correlated with the degree of decrease in FEV(1) with exercise. The purpose of our study was to examine whether eNO measurements prior to or after exercise could be used as a surrogate marker of exertional bronchoconstriction in a population referred specifically for the evaluation of EIB.


METHODS
We studied 50 consecutive subjects without a history of asthma who were referred for the clinical evaluation of EIB. eNO levels were measured prior to exercise challenge and every 5 min for a total of 30 min after exercise. Forced expiratory flows were measured prior to and serially after exercise challenge.


RESULTS
Seven subjects had a decrease in FEV(1) of > or = 15% with exercise. The mean eNO level prior to exercise was 41 parts per billion (ppb) [median +/- SD, 23 +/- 42.2 ppb] in the EIB group and 25.6 ppb (median, 19.95 +/- 18.47 ppb) in the group without EIB. A receiver operator characteristic curve yielded a value of 0.636. When using an eNO level of < 12 ppb, the sensitivity, specificity, negative predictive value, and positive predictive value for EIB were 1.0, 0.31, 0.19, and 1.0, respectively; therefore, no one with a baseline eNO of < 12 ppb demonstrated EIB.


CONCLUSIONS
No subjects with very low pre-exercise eNO levels (< 12 ppb) demonstrated bronchial hyperresponsiveness to exercise. eNO measurement may obviate the need for bronchoprovocation testing in patients who complain of exertional dyspnea.
ElHalawani
Samy M
SM
Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, Naval Medical Center San Diego, San Diego, CA 92134, USA.
Ly
Nam T
NT
Mahon
Richard T
RT
Amundson
Dennis E
DE
D000328:Adult; D001250:Asthma, Exercise-Induced / Q000175:diagnosis* / Q000378:metabolism; D015415:Biomarkers; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D011237:Predictive Value of Tests; D012372:ROC Curve
D015415:Biomarkers; D009569:Nitric Oxide