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Fractional Exhaled Nitric Oxide measurement for diagnosing asthma and predicting steroid responsiveness - a systematic review


Principal Investigator: Antonius Schneider, university hospital Klinikum rechts der Isar (on the right of the river Isar) of Technische Universität München

Funding: BMBF

Project members: Dr. rer. nat. Gerta Rücker, Dipl. Math Harriet Sommer



Asthma is a common chronic disease with a high prevalence of approx. 5%. It is characterised by a
chronic inflammation process which induces bronchial hyper-responsiveness (BHR) and usually reversible airway obstruction. Spirometry is the reference standard for diagnosing airway obstruction. In mild asthma, airway obstruction is often not present, thus leading to diagnostic uncertainty. In that case, bronchial provocation remains as a reference standard for determining BHR. However, bronchial provocation is only available in specialised centres and carries a small risk of inducing severe bronchospasm. Patients with asthma have high levels of nitric oxide in their exhaled breath which correlates with the inflammation process and steroid responsiveness. Measurement of fractional exhaled nitric oxide (FENO) is a non-invasive method for diagnosing asthma. Increased FENO concentrations have been found in asthmatic patients including those with mild disease. It has been claimed that FENO
measurement would help to make or exclude asthma safely and fast without performing bronchial provocation. Due to the heterogeneous results it remains unclear, how to interpret test results of FENO measurement in terms of diagnosing asthma and to determine steroid responsiveness. The recommended cut-off values are based on single study results, which are summarized in a narrative way. The aim of the systematic review is to investigate the diagnostic accuracy of FENO measurement for diagnosing asthma and to determine the diagnostic accuracy for predicting steroid responsiveness.