Variability of FeNO in healthy subjects at 2240 meters above sea level

Abstract

Fraction of exhaled nitric oxide (FeNO) is a marker of eosinophilic airway inflammation. Altitude above sea level can affect measurements of this index, but there is only limited information regarding the diurnal variation (ante meridiem vs. post meridiem) and reproducibility of FeNO on consecutive days at moderate altitudes. To evaluate the diurnal variability of FeNO and assess its reproducibility over five consecutive days in healthy individuals living at 2240 m, and to compare the FeNO readings taken with two different analyzers. Healthy non-smoking adults were measured using NIOX MINO(®) or NOA 280i(®) devices. One group (n = 10) had readings taken morning and afternoon for five consecutive days with the NIOX MINO(®) equipment; while the second group (n = 17) was measured on only one morning but by both the electrochemical analyzer (NIOX MINO(®)) and the chemiluminescence method (NOA 280i(®)). The study group consisted of 27 subjects aged 28.7 ± 6 years. Morning and afternoon FeNO measurements were 15.2 ± 7.5 ppb and 15.2 ± 7.9 ppb (p = 0.9), respectively. The coefficient of variation (CV) of these measurements (a.m. vs. p.m.) was 10.7 %, and the coefficient of repeatability (CR), 4.2 ppb. The concordance correlation coefficient (CCC) between the two measures (morning vs. afternoon) was 0.91. The CV and CR of the five morning readings were 15.4 % and 4.3 ppb, respectively; while those of the five afternoon measures were 13.6 % and 3.5 ppb, respectively. The CCC between the NIOX MINO(®) equipment and the NOA-280i(®) device was 0.8, with 95 % limits of agreement of -8.35 to 0.29 ppb. In adults living at 2240 m above sea level, FeNO measurements show minimal diurnal variation, and readings are reproducible (<15 %) over a period of at least five consecutive days; however, the FeNO measurements obtained with the NIOX MINO(®) and NOA 280i(®) devices are not interchangeable due to the wide limits of agreement recorded.

Exhaled nitric oxide in ethnically diverse high‐altitude native populations: A comparative study

“…The NIOXMINO uses a disposable electrochemical sensor and was developed commercially for use in a clinical setting around the management of airway inflammation and asthma. The main issue with the NIOX MINO system is that it cannot be calibrated, and indeed there has been considerable debate in the literature around the external validity of NIOX MINO measurements, particularly at altitude where only one validation study exists to support use of the device under low barometric pressure conditions (Beall et al, ; Gochicoa‐Rangel et al, ; Hemmingsson et al, ; Laskowski et al, ). From this, it is clear that NIOX MINO measures are not interchangeable with Siever's measures and it is fair to question the validity of the results presented in this article.…”

“…That is, the device shows high repeatability and use of calibration for the chemiluminescence analyzer (Brody et al, ; Choong & David, ; Olin et al, ; Travers et al, ). Only one validation study supports the use of the NIOX MINO at high altitude (Gochicoa‐Rangel et al, ). The latter study compared the NIOX MINO® to the Sievers NOA 280i® and reported a high correlation (0.96, p < .001) between the two measurement devices (participants were healthy nonsmoking adults of Mexico City, Mexico, measured at an altitude of 2,240 m above sea level).…”

The Effect of Physical Activity on Spirometry and Fractional Exhaled Nitric Oxide in Adolescents—Longitudinal Study

“…The current knowledge regarding the diurnal FeNO variability shows its minimal variation. In five subsequent days, the FeNO coefficient of variation (CV) in the morning was 15.4% and 13.6% in the evening in the healthy subjects located at 2240 m above the sea [15]. Other researchers suggest slight FeNO variation with the highest values in the morning and the lowest values in the evening [16].…”

Predictive meaning of Fractional Exhaled Nitric Oxide (FeNO) in the diagnosis of asthma for epidemiological purposes – an 8-year follow-up study

“…The 20% of the variability was explained by age, rhinoconjunctivitis, positive skin prick test and removal of cat and/or dog from the house [25]. The internal variability (within the group) of FeNO seems to be stable according to current litera-ture [26,27] and should not impact the differences between the status of children.…”