Background: Several studies reported low nasal nitric oxide (nNO) levels in subjects with primary ciliary dyskinesia (PCD) and proposed nNO measurement as a diagnostic tool to screen for the disease. All these reports used the aspiration nNO method. The goal of this study was to evaluate nNO in patients with PCD using different methods of NO measurement, including continuous aspiration, silent exhalation, and single-breath humming exhalation, which increases NO wash-out from the paranasal sinuses to the nose.
Material/methods: Fourteen patients with established diagnosis of PCD and 14 healthy controls (HC) were examined. Oral and nasal NO levels were measured by chemiluminescence. Each subject performed NO measurement in triplicate during oral exhalation, nasal aspiration (nNOasp), nasal exhalation (nNOexh), and single-breath humming (nNOhum).
Results: The median nNOasp value (95% confidence interval) was 11.6 (7.2-19.1) ppb in PCD and 321.8 (270.6-510.6) ppb in HC (p<0.001). The nNOexh value was 2.2 (1.3-3.1) in PCD and 31.8 (26.6-47.2) ppb in HC (p<0.001). Patients with PCD had lower nNO than HC during the last 80% of the exhalation throughout humming, i.e. 2.8 (2.2-4.3) ppb vs. 212.4 (158.7-244.8) ppb (p<0.001), and did not show a clear nNO peak. All nasal NO measurements had excellent specificity and sensitivity in detecting PCD compared with the healthy controls.
Conclusions: nNO is consistently low in PCD with good specificity and sensitivity whatever the method used for NO measurement. The extremely low levels of nNO during humming support the notion that NO is defective in the paranasal sinuses in PCD.