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Repeated Fractional Exhaled Nitric Oxide Measurements Is Not Essential for Asthma Screening

Yeon Yang S1, Hee Kim Y2, Kwang Byun M1, Jung Kim H1, Min Ahn C1, Han Kim S1, Sun Lee H3, Jung Park H*4

1Department of Internal Medicine, Gangnam Severance Hospital
2Department of Pediatrics, Gangnam Severance Hospital
3Biostatistics Collaboration Unit
4Department of Internal Medicine, Yong-in Severance Hospital
Yonsei University College of Medicine, Seoul, Korea

J Investig Allergol Clin Immunol 2018; Vol. 28(2)
doi: 10.18176/jiaci.0215

Background: Although older guidelines recommend that fractional exhaled nitric oxide (FeNO) should be checked more than twice during the same session for an asthma diagnosis, recent studies showed the excellent reproducibility of FeNO measurements.
Objective: We aimed to determine whether repeated FeNO measurements during the same session are necessary for asthma screening.
Methods: We retrospectively reviewed the electronic medical records of adult outpatient subjects who visited the pulmonary department for an asthma diagnosis and assessed FeNO measurements obtained from June 2016 to July 2017.
Results: Among the total of 132 enrolled patients, 79 patients (59.8%) were diagnosed with asthma. Repeated FeNO measurements taken during the same session showed high reproducibility (intraclass correlation coefficient > 0.9; P < 0.001) and a strong correlation (Pearson’s coefficient > 0.9; P < 0.001); however, the reproducibility and correlation were slightly weaker in subjects with low FeNO values. The value of repeated measurement was not significantly different each other in general; however, the second FeNO measurement was significantly higher than the first measurement in subjects with the lowest and highest lung function. The predictive power of FeNO for asthma measured the first time (sensitivity, 80.5%; specificity, 85.1%) was not inferior to that measured the second time (sensitivity, 76.6%; specificity 85.1%) or the even geometric mean of the two.
Conclusion: Repeated FeNO measurement during the same session is not essential for asthma screening in cases when the first acceptable FeNO measurement is performed using the proper method.

Key words: Asthma, Fractional Exhaled Nitric Oxide, Repeated measurements