Usefulness of Exhaled Nitric Oxide and Sputum Eosinophils in the long-term control of Eosinophilic Asthma

Background: The aim of the present study was to treat unstable asthma according to exhaled nitric
oxide (eNO) and induced-sputum eosinophils (sEos) levels to assess if this strategy is better than the
conventional approach based on symptoms and function to achieve asthma control.
Methods: Fourteen patients with mild-to-moderate persistent asthma (6 men, 8 women) were
recruited. During the recruitment visit, the patients, previously treated for asthma following Global
Initiative for Asthma recommendations, underwent clinical evaluation and pulmonary function tests
(PFTs). Then, after 4 weeks of washout from inhaled antiinflammatory treatment, the patients
underwent a basal visit performing PFTs, challenge test to methacholine, and determination of eNO
and sEos counts. These procedures were repeated after 3, 6, and 12 months while the patients were
treated with inhaled steroids in a stepwise fashion according to eNO and sEos values.
Results: At the end of the study, a significant decrease in eNO and sEos was observed (57.2 32.8
parts per billion [ppb] vs 22.1 10.8 ppb, p < 0.01; and 27.1 27.1% vs 3.7 3.5%, p < 0.01,
respectively). A close correlation (r2 0.41, p < 0.01) between the percentage change of eNO and
sEos was observed only after 6 months. Patients treated according to the levels of these inflammatory
markers had fewer symptoms and fewer exacerbations compared to those the year before when they
were conventionally treated.
Conclusions: Our results show the usefulness of eNO and sEos for titrating treatment in asthmatic
patients in order to achieve better long-term control of the disease. The eNO decrease reflects
adequately the reduction of sEos only after 6 months.