Nasal nitric oxide for early diagnosis of primary ciliary dyskinesia: practical issues in children.

BACKGROUND: Primary ciliary dyskinesia (PCD) is a genetic disease characterized by abnormally beating cilia. In these patients, levels of nasal nitric oxide (nNO) are lower than those observed in healthy subjects. OBJECTIVES: We identify the nNO levels in healthy pre-school uncooperative children and in PCD patients, in order the application of nNO measurement in the early identification of young children with PCD. METHODS: We measured nNO in 77 healthy children (50 uncooperative and 27 cooperative) and in 10 PCD patients. Fifteen cooperative healthy children were also asked to perform an uncooperative test. RESULTS: PCD patients presented low nNO levels (29.7+/-5.7 ppb) compared to those observed in healthy children (358.8+/-35.2 ppb; p<0.05). nNO levels were increased in healthy cooperative children (650+/-60.6 ppb; p<0.05) as compared to those uncooperative aging more than 6 month (309.1+/-45.9 ppb; p<0.05) or less (128.1+/-16.2 ppb; p<0.05). Twenty-four uncooperative children with nNO values < or = 200 ppb performed a second evaluation at least 6 months later and mean levels increased from 104.7+/-10.5 ppb to 169.9+/-19.6 ppb (p<0.05). In the 15 collaborative children nNO levels were higher during the breath holding manoeuvre (687.7+/-96.9 ppb) than during the tidal breathing manoeuvre (335.9+/-57.9 ppb; p<0.05). CONCLUSIONS: Healthy children have higher nNO levels than PCD patients. In 15% of uncooperative healthy children can be found low nNO levels, similar to PCD patients, but those values increased some months later, in successive evaluations. Nasal NO may be used for PCD screening even though repeated evaluations may be necessary in young children.