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However, the major advantage of using measurements exhaled NO, particularly over sputum
eosinophil counts, blood tests or airway challenges is obvious -
particulady in children. It is a
non-invasive test, analogous to lung function testing to which patients are very familiar' It is
also likely to be available in more clinics and can be performed more quickly and more
cheaply with immediate results.
g.g Nitric oxide levels in primar.v ciliary dyskinesia
This is an area where NO measurement was found early to be of particular value. Initially No
was found to be absent in nasal measurements in four children with Kartagener's syndrome
(Lundberg, Weitzberg et al. 1994). This led to the evaluation of 21 children with primary
ciliary dyskinesia (PCD) in whom both nasal and oral NO was found to be significantly lower
when compared to 60 healthy children. While there was some overlap with regard to
individual lower airway results, only one child was an outlier from each group in the nasal
NO ranges (Karadag, James et al. 1999). This has been confirmed in a recent study where the
impairment of NO output was less pronounced in lower than the upper nasal respiratory tract
after sampling at several sites in 17 PCD and 28 healthy subjects (Matrut, Escudier et al.
2006). In another large cross-sectional study involving 102 subjects, the concentration of
exhaled NO was significantly lower in both PCD and CF patients than bronchiectasis and
healthy subjects. The nasal NO, however, was markedly reduced only in the PCD subjects
(Horvath, Loukides et al. 2003). This change appears to occur early in life as seen in two
infants with pCD aged four and six months having significantly lower levels of NO compared
to five healthy controls (Baraldi, Pasquale et a|.2004). These low NO levels found are despite
levels of nitrite, nitrate and S-nitrosothiol when measured in exhaled breath condensate being
no different from normals (Csoma, Bush et al. 2003)'
Use of NO as a screening tool for this condition has been investigated. From the study above
reviewing children already diagnosed with PCD, the authors determined a cut off of 250ppb
for nasal NO as having both a positive and a negative predictive value of 0.95. This correctly
detected 20 of 21 subjects as having PCD and conectly detected 19 of 20 as not having PCD
(Karadag, James et al. Lggg). Measuring 31 children with PCD, 2l with non-CF
bronchiectasis, 17 with CF, 35 with asthma and 53 healthy controls, a nasal NO of 250ppb
gave a sensitivity of 977o and a specificity of gOVo for a diagnosis of PCD (Narang, Ersu et al'
2OOZ). Of 34 children referred for investigation for possible PCD to a tertiary clinic, the 17
that proved positive on biopsy again had significantly lower level of nasal NO. This group
determined a nasal NO of 105ppb gave a specificity of 88Vo and a positive predictor value of
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