Exhaled nitric oxide measurement is not useful for predicting the response to inhaled corticosteroids in subjects with chronic cough.
BACKGROUND
Increased concentrations of exhaled nitric oxide (ENO) are identified predominantly in subjects with chronic cough due to conditions that habitually respond well to therapy with inhaled corticosteroids (ICSs). The aim of this study was to assess the usefulness of ENO in predicting the response to ICS therapy in subjects with chronic cough and to determine the relationship between either methacholine or adenosine 5'-monophosphate (AMP) responsiveness and the response to ICS therapy.


METHODS
A total of 43 patients with chronic cough were studied. During the baseline period, ENO measurement, spirometry, and concentration-response studies with both methacholine and AMP were performed. For the next 4 weeks, the patients were treated with inhaled fluticasone propionate, 100 microg twice daily. At baseline (1 week) and during the 4-week treatment period, patients twice daily completed entries in a diary, in which they recorded daytime and nighttime cough symptom scores.


RESULTS
Nineteen patients (44%) responded well to fluticasone therapy. The receiver operating characteristic curve analysis showed that the accuracy of identifying the response to ICS therapy for ENO at baseline was poor. The sensitivity and specificity of ENO for predicting the response to ICS therapy, using 20 parts per billion as the ENO cutoff point, were 53% and 63%, respectively. Differences in both prevalence and degree of airway responsiveness to either methacholine or AMP between fluticasone-responsive subjects and nonresponsive subjects were also not significant.


CONCLUSIONS
Although a significant proportion of subjects with chronic cough respond well to ICS therapy, these patients cannot be identified by ENO levels or AMP responsiveness at baseline.
Seccion de Alergologia, Asociación Valenciana de Investigaciones Clinicas, Valencia, Spain. Electronic address: prieto_jes@gva.es.
Luis
L
Prieto
Seccion de Alergologia, Asociación Valenciana de Investigaciones Clinicas, Valencia, Spain.
Anna
A
Ferrer
Servicio de Neumologia, Hospital Universitario Dr. Peset, Valencia, Spain.
Silvia
S
Ponce
Servicio de Neumologia, Hospital Universitario Dr. Peset, Valencia, Spain.
Julio
J
Palop
Universidad de Valencia, Valencia, Spain.
Julio
J
Marín
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000368:Aged; D000730:Androstadienes / Q000008:administration & dosage*; D001985:Bronchial Provocation Tests; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D002908:Chronic Disease; D003371:Cough / Q000188:drug therapy*; D005260:Female; D000068298:Fluticasone; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013147:Spirometry
D000730:Androstadienes; D001993:Bronchodilator Agents; D016210:Methacholine Chloride; D009569:Nitric Oxide; D000249:Adenosine Monophosphate; D000068298:Fluticasone