Benefit of inhaled corticosteroids (ICS) in asthmatic patients with bronchial hyperresponsiveness (BHR) to mannitol and low fractional exhaled nitric oxide (FeNO) levels

Abstract

<b>Introduction:</b> Asthmatics with BHR to mannitol demonstrate clinical benefit with regular ICS. It has been demonstrated FeNO should be &gt;47ppb for clinical benefits to ICS. However, it has been observed that many with BHR to mannitol have ‘normal’ (0-24ppb) or ‘borderline’ (25-47ppb) FeNO levels, suggesting no benefit with ICS. <b>Aim:</b> To determine if a clinical benefit is observed with ICS in uncontrolled asthmatics with BHR to mannitol that have FeNO levels ≤47ppb. <b>Methods:</b> Adult asthmatics (n=20) who were referred to a pulmonary function laboratory for an assessment of BHR to inhaled mannitol also performed FeNO and the Asthma Control Questionnaire (ACQ). All participants entered the study with an ACQ score &gt;0.75, indicating uncontrolled asthma. Following regular ICS for 6 weeks, FeNO and ACQ scores were reassessed. <b>Results:</b> Patients (n=20, median age 36yrs (range:18-71), 7F;13M) had moderate BHR to mannitol (GeoMean PD₁₅ 81mg, 95% CI 52-126), mean FeNO of 32ppb and an ACQ score of 1.75. The majority (85%) had FeNO &lt;47ppb (8 normal; 9 borderline). ICS for 6 weeks afforded a clinically significant decrease in ACQ score to 0.86 (Δ0.89, p&lt;0.001), associated with a reduction in mean FeNO to 18 ppb (p=0.007). Clinical benefit was also seen when the normal/borderline (&lt;47ppb) group were analysed separately with a decrease in ACQ score to 0.95 (Δ0.81, p&lt;0.001). <b>Conclusion:</b> Clinically significant benefit to ICS was observed in patients with uncontrolled asthma and BHR to mannitol with borderline to normal FeNO levels. This suggests there is a low FeNO phenotype in asthma that is ICS sensitive.