Nasal nitric oxide (nNO) has a well-known potential as indirect discriminative marker between patients with primary ciliary dyskinesia (PCD) and healthy subjects, but real-life experience and usefulness in young children is sparsely reported. Three nNO sampling methods were examined and compared as first-line tests for PCD. Healthy subjects, confirmed PCDs, consecutive referrals with PCD-like symptoms and patients with cystic fibrosis (CF) had nNO sampled during breath hold (BH-nNO), oral exhalation against resistance (OE-R-nNO), and tidal breathing (TB-nNO) aiming to expand age range into infancy. 282 subjects, 117 consecutive referrals, 59 PCDs, 49 CF patients and 57 healthy were included. All methods separated significantly between PCD and non-PCD including CF with reliability in ranking order BH-nNO > OE-R-nNO > TB-nNO. Acceptability in children ranked in reverse order. A problematic high fraction (39%) of false positive TB-nNO was found in young children. An unexpected large fraction (6.8%) of PCDs had nNO values above cut-off. Nasal NO is a helpful first-line tool in real-life PCD work-up in all age groups if sampling method is chosen according to age. nNO can be misleading in a few patients with true PCD. Further studies are strongly needed in young children.
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Bloch et al. (1979) studied this question.