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season and then reduced down to baseline. However, their exhaled NO did not necessarily
correlate with FEV1 @araldi, Carra et al. 1999). Exhaled NO did relate to recent symptoms
versus no symptoms when dividing 133 children aged 5-14 years attending a hospital clinic
into 'uncontrolled' and 'controlled' asthma groups. The researchers also felt that NO
predicted subgroups as to whether IHCS or medication was increased, decreased or remained
unchanged (Warke, Mairs et al. 2004).
There have also been studies where exhaled NO was measured prospectively while IHCS
doses were reduced. After three months of good control on moderate doses of IHCS (500-
1000pg/day beclomethasone), 37 asthmatics had their individual doses halved for twelve
weeks. Parameters which detected the ten that developed an exacerbation were; a baseline
exhaled NO level > 20ppb, or a baseline exhaled NO level > l5ppb plus a bronchoconstriction
response to the adenosine S-monophosphate challenge, or a rapid increase in exhaled NO over
the first weeks of the assessments (Prieto, Bruno et al. 2003). In 78 asthmatic adults, IHCS
treatment was withdrawn over six weeks with 60 subjects developing symptoms. Both the
baseline measurement of exhaled NO and an increase of 60Vo over the baseline reading had
positive predictive values between 80-90Vo for an exacerbation and was similar to the
predictive values using sputum eosinophils or hypertonic saline airway responsiveness (Jones,
Kittelson et al. 2001). Similarly, nine of 40 children with a mean age of 12.2 years relapsed 2-
4 weeks after withdrawal of steroids. The exhaled NO was higher at a mean of 35.3ppb versus
15.7ppb at two weeks and 40.8ppb versus l5.9ppb at four weeks. A value of 49ppb at four
weeks after steroid discontinuation had the best sensitivity at TLVo and specificity at 93Vo for
an asthma relapse @ijnenburg, Hoftruis et al. 2005). One study was less conclusive.
Seventeen moderate asthmatic adults had their daily dose of IHCS halved at 20 day intervals
until loss of control or replacement with placebo. Of the parameters which were measured
every ten days, the sputum eosinophil percentage altered 20 days ahead of deterioration while
changes in exhaled NO, FEVr and methacholine PC26 were only observed once symptoms had
already developed @elda, Parameswaran et al. 2006).
Studies have also compared changes in exhaled NO with traditional clinical and lung function
assessments to dictate changes in treatment.ln 97 adult asthmatics, future treatment decisions
regarding steroid adjustment were assigned randomly to be based either on exhaled NO levels
q! on an algorithm based on the conventional GINA 2OO2 guideline (GINA 2002). The
optimal IHCS dose per individual was determined in the first phase and patients were then
followed for L2 months. The mean final doses of inhaled fluticasone used were 3701tglday for
the 46 patients in the exhaled NO group and 64Lltglday for the 48 patients in the guideline
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