Background: Exhaled nitric oxide (FENO) measurements may help to highlight when inhaled corticosteroid (ICS) therapy should or should not be adjusted in asthma. This is often difficult to judge. Our aim was to evaluate a decision-support algorithm incorporating FENO measurements in a nurse-led asthma clinic.
Methods: Asthma management was guided by an algorithm based on high (>45ppb), intermediate (30-45ppb), or low (<30ppb) FENO levels and asthma control status. This provided for one of eight possible treatment options, including diagnosis review and ICS dose adjustment.
Study measurements at each visit: FENO was measured according to current guidelines19 using a NIOX MINO electrochemical analyser20-22 or a NIOX chemiluminescence analyser (both Aerocrine, Solna, Sweden). The latter was available at the Research Unit, 5km. from the Health Centre, but was used only when there was technical failure of the NIOX MINO. To validate FENO results, the sensors from the NIOX MINO device were tested against a calibrated standard, and where appropriate, a correction factor was applied to take account of signal drift. Spirometry was performed according to accepted standards using a Spiro USB spirometer (Micro Medical, Kent, England). The study received ethical approval from the Lower South Island Ethics Committee, and each participant gave written informed consent. Each GP participated in a start-up meeting, but thereafter further directions regarding the conduct of the study were not given.