The value of nasal nitric oxide measurement in the diagnosis of primary ciliary dyskinesia

Importance Nasal nitric oxide (nNO) testing is a method used in the diagnosis of primary ciliary dyskinesia (PCD). It has not been evaluated in Chinese population. Objective To establish a reference nNO value to assist in the diagnosis of PCD in Chinese children. Methods nNO values were measured in children with PCD (n = 36), cystic fibrosis (CF) (n = 20), asthma (n = 45), post‐infectious bronchiolitis obliterans (BO) (n = 41) and non‐PCD/non‐CF bronchiectasis (n = 32). The receiver operating characteristic nNO value for the diagnosis of PCD was plotted and the area under the curve was calculated. Results nNO values were significantly lower in children with PCD (median 25.66 nL/min) than in children with asthma (186.26 ± 58.95 nL/ min), BO (143.47 ± 49.71 nL/min) and non‐PCD/non‐CF bronchiectasis (173.13 ± 63.80 nL/min), but not in children with CF (90.90 ± 43.20 nL/min). Notably however, no CF patient had an nNO value < 45 nL/min. A cut‐off of 76 nL/min yielded the best sensitivity of 86.1%, and specificity of 91.4%, with an area under the curve of 0.920 (95% confidence interval 0.859–0.981) for the diagnosis of PCD. If CF was ruled out the specificity increased to nearly 100%. Interpretation nNO testing is able to discriminate between patients with PCD and those with CF, asthma, post‐infectious BO and non‐PCD/non‐CF bronchiectasis. A cut‐off of 76 nL/min could be further examined in patients suspected of PCD, to establish an nNO reference value for PCD screening in Chinese children.