Measurement of Fractional Exhaled Nitric Oxide: Comparison of Three Different Analysers

Abstract

Background: Fractional exhaled nitric oxide (FeNO) is a surrogate marker for airway inflammation, supporting the diagnostic pathway and treatment decisions for asthma patients. Objectives: Aim of this study was to compare the new analyser Vivatmo pro (Bosch, BV) with NIOX VERO (Circassia, CN) and CLD (Ecomedics, EC). Methods: In 100 asthmatics (median 53 years [range 20–87], 62% female, 86% on inhaled corticosteroids [mean 1,300 μg beclomethasone dipropionate or equivalent], 35% treated with biologics) 2 FeNO measurements per device were performed. Additionally, the success rate to achieve a valid NO value was evaluated. Results: Sixty-eight percent of the patients had FeNO values below 50 ppb. Median NO concentrations were 31 ppb (range 6–194) for BV, 33 ppb (9–164) for CN and 31ppb (7–353) for EC. Bland-Altman plots suggested an agreement within the predefined limits of ±5 ppb for all analysers within the therapeutically relevant range (0–70 ppb). The highest agreement in FeNO levels were between BV and EC with mean differences of –0.26 (95% CI –1.48 to 0.95) vs. 1.52 (95% CI 0.4–2.6) ppb for CN and EC. The results indicate an equivalence of the methods (two-one sided t test-equivalence test: p < 0.0001, ±5 ppb margins). Acceptance of the measurements was high for all devices (97%). The highest success rate to obtain 2 valid NO values without failed attempts was achieved with the BV analyser (73 vs. 62% for the CN analyser and 46% for the EC analyser). Conclusions: For the range between 0 and 70 ppb, FeNO concentrations measured with all 3 devices were statistically equivalent within predefined acceptance criteria and did not differ in a clinically relevant way.