Chest
Volume 131, Issue 6, June 2007, Pages 1852-1856
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ORIGINAL RESEARCH
EXHALED NITRIC OXIDE
Fraction of Exhaled Nitric Oxide at 50 mL/s: Reference Values for Adult Lifelong Never-Smokers

https://doi.org/10.1378/chest.06-2928Get rights and content

Background

The measurement of fractional exhaled nitric oxide (FENO) is used as a marker of airway inflammation. The aim of this study was to establish reference values of FENO for adults.

Methods

FENO at a flow rate of 50 mL/s was analyzed in 3,376 adults using a chemiluminescence analyzer according to American Thoracic Society/European Respiratory Society guidelines. Blood samples were analyzed, and atopy was defined as the presence of specific IgE. All subjects responded to a respiratory questionnaire. Those who had never smoked (n = 1,803) were selected for this study. After the exclusion of subjects with physician-diagnosed asthma, asthma symptoms, ever wheezing, dry cough, or use of inhaled steroids, 1,131 healthy never-smokers remained, including 845 nonatopic and 286 atopic subjects.

Results

Based on multiple regression modeling, we propose the following reference equation for healthy never-smoking adults: Ln(FENO) = 0.057 + 0.013 × height (in centimeters) + 0.0088 × age (in years). The residual SD was 0.51, and the explanatory value was 9%. In a model, based on nonatopic subjects alone, the reference equation obtained was slightly different, as follows: Ln(FENO) = −0.0026 + 0.013 × height (in centimeters) + 0.010 × age (in years). The residual SD for this equation was 0.48, and the explanatory value was 11%.

Conclusions

Normal values of FENO for adults may be predicted on the basis of age and height. However, as the reference equations only account for about 9 to 11% of the variation, the most important information that could be extracted from the study is that the upper limits of FENO range from 24.0 to 54.0 parts per billion, depending on age and height.

Section snippets

Materials and Methods

A general population sample of men and women who were 25 to 75 years old was randomly selected from the population register in Göteborg, Sweden. Between April 2001 and November 2005, FENO was investigated in 3,376 adult subjects. All subjects received a postal questionnaire and an invitation to undergo a clinical examination, as previously described.10 Those who had never smoked (n = 1,803) were selected for this study. Of these, 507 subjects reporting physician-diagnosed asthma,11 asthma

Results

Table 1 presents basic data about the subjects. The geometric mean of FENO for the whole population was 16.6 ppb (95% RI, 5.87 to 47.14). FENO was higher among subjects with atopy, 18.8 ppb (95% RI, 6.03 to 58.74) compared to 16.0 ppb (95% RI, 5.91 to 58.76) among nonatopic subjects. FENO was higher among men (18.5 ppb; 95% RI, 16.67 to 51.13) compared to women (14.9 ppb; 95% RI, 5.36 to 41.52). However, when comparing men and women with similar height and age, FENO was similar between the

Discussion

This study gives reference equations for predicted normal FENO for adults, based on 1,131 healthy never-smokers from a random general population sample. As previously shown, age and height are significant explanatory variables, but sex is not when height is allowed for. Our study contributes new knowledge as it is the first study that has outlined reference values according to age and height among adults.

The equations have a low explanatory value resulting in wide RIs. The equations explained

References (19)

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Cited by (156)

  • Parallel gradients in F<inf>ENO</inf> and in the prevalences of asthma and atopy in adult general populations of Sweden, Finland and Estonia — A Nordic EpiLung study

    2020, Respiratory Medicine
    Citation Excerpt :

    Nevertheless, we employed similar FENO devices and applied a validated conversion model to standardise FENO to the recommended expiratory flow of 50 mL/s [21] to obtain comparable values. The standardised FENO values are similar to those obtained in large general populations studies [46] and also by applying a reference equation to our pooled population [47]. The FENO value obtained in Örebro in the present study is in harmony with the values found in a general population study from Gothenburg in Sweden [44], which employed the recommended expiratory flow of 50 mL/s.

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The study was supported by the Swedish Council for Work Life and Social Research (FAS), the Swedish Heart and Lung Foundation and Astra-Zeneca, Sweden.

The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

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