A comparison of exhaled nitric oxide measurements performed using three different analysers.
BACKGROUND
Exhaled nitric oxide (NO) is an established technique for monitoring airway inflammation. We have compared exhaled NO measurements from 3 different analysers; Ecomedics (E), Niox (N) and Logan (L).


METHODS
Thirty subjects (10 non-smoking healthy subjects, 10 non-smoking patients with asthma and 10 ex-smoking COPD patients) performed 3 repeated measurements of exhaled NO at a flow rate of 50 ml/s on each of the 3 analysers. Within analyser variability was determined by calculating the repeatability coefficient for each analyser. Differences between analysers were assessed by (1) the differences between group means and (2) the Bland Altman method to estimate the variability expected for an individual using the 3 analysers.


RESULTS
The repeatability coefficients (expressed as ratios) were 1.12, 1.19 and 1.19 for N, E and L, respectively. There were significant differences (P<0.05) between analysers; the Logan analyser gave the highest group mean values and Ecomedics gave the lowest group mean values. Differences between analysers were observed in all subject groups (healthy, asthma, COPD). Similar results were obtained in the 3 groups when analysed separately. Bland Altman analysis gave the following ratios [data are mean ratio (95% limits of agreement)]; N:E 1.59 (1.02-2.50), L:N 1.23 (0.72-2.13), L:E 1.96 (1.09-3.57).


CONCLUSIONS
Our findings indicate that exhaled NO measurements in healthy subjects and patients with airways disease differ according to the type of analyser used.
Borrill
Zoë
Z
Medicines Evaluation Unit, North West Lung Centre, Wythenshawe Hospital, Southmoor Road., Manchester M23 9LT, UK. zborrill@meu.org.uk
Clough
David
D
Truman
Nick
N
Morris
Julie
J
Langley
Stephen
S
Singh
Dave
D
D000328:Adult; D000368:Aged; D001249:Asthma / Q000378:metabolism*; D001944:Breath Tests / Q000295:instrumentation; D045853:Exhalation; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000032:analysis*; D015203:Reproducibility of Results
D009569:Nitric Oxide