Diagnostic utility of inflammatory biomarkers in asthma: exhaled nitric oxide and induced sputum eosinophil count

Respir Med. 2007 Nov;101(11):2416-21. doi: 10.1016/j.rmed.2007.05.019. Epub 2007 Aug 21.


Background: Even though an inflammatory process is known to be the underlying cause of asthma, diagnosis is based on clinical history, reversible airway obstruction and bronchial hyperresponsiveness according to international guidelines. The fraction of exhaled nitric oxide (FE(NO)) and induced sputum eosinophil count (Eos%) have been used as non-invasive inflammatory biomarkers.

Objectives: The aim of this study was to compare the sensitivity and specificity of FE(NO), Eos% and spirometry and to assess whether their combined use in clinical practice would improve diagnostic yield.

Methods: In 50 patients with asthma symptoms we performed spirometry, a methacholine challenge test, FE(NO) measurement and assessment of Eos% in induced sputum. The standard diagnosis of asthma followed the guidelines of the Global Initiative for Asthma.

Results: Twenty-two of the 50 patients were diagnosed with asthma. The sensitivity and diagnostic accuracy were higher for FE(NO) measurement (77%; area under the receiver operating curve [AUC], 0.8) than for spirometry (22%; AUC, 0.63). The sensitivity and specificity of Eos% in induced sputum were 40% and 82%, respectively, and the diagnostic accuracy of Eos% was lower (AUC, 0.58). When both inflammatory biomarkers were used together specificity increased to 76%.

Conclusions: The diagnostic accuracy of FE(NO) measurement was superior to that of the standard diagnostic spirometry in patients with symptoms suggestive of asthma. The use of FE(NO) measurement and induced sputum Eos% together to diagnose asthma in clinical practice is more accurate than spirometry or FE(NO) assessment alone and easier to perform.

Publication types

  • Comparative Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Asthma / diagnosis*
  • Asthma / metabolism
  • Breath Tests
  • Bronchial Provocation Tests / methods
  • Eosinophils*
  • Female
  • Forced Expiratory Volume / physiology
  • Humans
  • Leukocyte Count
  • Male
  • Middle Aged
  • Nitric Oxide / analysis*
  • Prospective Studies
  • Sensitivity and Specificity
  • Spirometry
  • Sputum / cytology*


  • Nitric Oxide