LAUSR

Nasal nitric oxide (nNO) measurement is a first-line test used to increase the post-measurement probability of primary ciliary dyskinesia (PCD) in subjects with symptoms consistent with this diagnosis [1]. The accuracy of nNO measurement is essential since it will orientate the work-up towards tests that are usually highly specialised and sometimes invasive. Accuracy of biological measurements relies on the technical and on the biological variability. While the accuracy of NO analysers is known better for chemiluminescence devices (e.g. <1 ppb with 1% linearity from 0.1 to 5000 ppb for CLD 88 (Eco Medics, Duernten, Switzerland)) than for widely used electrochemical devices (e.g. ±5 ppb for values <50 ppb and 10% for values >50 ppb for Niox Vero (Circassia, Oxford, UK)) [2], little is known on the biological variability of nNO measurements, except for increased nNO output variability in adults with rhinitis compared with healthy subjects and the positive effect of training on the level of nNO taken during expiration against a resistance (nNO-ER) in children [3, 4]. A repeatability of 10% for NO measurements obtained with the velum closed in the same or both nostrils is relevant, while measurements taken during tidal breathing should aim for a repeatability of 20% and 30%, respectively https://bit.ly/3sMnug6