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[Fractional exhaled nitric oxide: validation of a 6 second exhalation time with two different analysers].

OBJECTIVE
To validate the measurement of fractional exhaled nitric oxide concentration (FE(NO)) using a 6-sec exhalation time in patients aged between 5 and 17 years with a stationary chemiluminescence analyser (NIOX, Aerocrine) and a portable electrochemical analyser (NIOX-MINO, Aerocrine).


MATERIAL AND METHODS
FE(NO) was assessed in 60 patients randomised into two groups. In Group 1 (n = 30, NIOX analyser), three valid FE(NO) measurements were obtained for two exhalation times (10 sec and 6 sec); the mean of the three measurements was recorded. In Group 2 (n = 30, NIOX-MINO), a single valid measurement of FE(NO) was obtained for each exhalation time. We analysed age, gender, weight, height, diagnosis, treatment, FE(NO) and the number of attempts with both exhalation times in each analyser. Agreement between FE(NO) assessed using 10-sec and 6-sec exhalations was assessed by Bland-Altman analysis and Cohen's kappa.


RESULTS
The mean (SD) age in Group 1 was 10.1 (3.07) years. The mean age in Group 2 was 10.43 (2.94) years. Bland-Altman analysis demonstrated good agreement between FE(NO) values obtained with both exhalation times and with both devices. Cohen's kappa, also demonstrated good agreement (NIOX, kappa = 1; NIOX-MINO, kappa = 0.93).


CONCLUSIONS
A 6-sec exhalation time is valid for measuring FE(NO) with both analysers in children aged over 5 years.