Exhaled nitric oxide and inhaled corticosteroid dose reduction in asthma: a cohort study

To the Editor: Inhaled corticosteroids (ICS) reduce airway inflammation; however, guidelines recommend titrating ICS dose based on symptoms [1], which are not closely associated with airway inflammation [2]. Once symptoms are controlled for ≥3 months, ICS reduction is recommended [3] but step-down is often not implemented. Studies suggest that the majority of patients treated with ICS can have their therapy stepped down, although there is no clear evidence on how best to achieve this [4]. We assessed whether exhaled nitric oxide fraction ( F eNO) measurements could predict a loss of symptom control or exacerbation following a reduction in ICS dose in a cohort study of people with well-controlled asthma recruited from primary care. All participants had a recorded asthma diagnosis, were aged 18–75 years, and had received at least one ICS prescription in the last year. The study was restricted to nonsmokers ( 1.5 at visit 1 (indicating poor control) were excluded. Participants were seen at the same time of day on four occasions: days 0, 14, 21 and 110. At each visit, ACQ-5, F eNO (Flex Flow; Aerocrine, Solna, Sweden) and spirometry were performed. Symptoms were assessed using the ACQ-5 [6]. Airway inflammation was measured using F eNO at 50 mL·s−1; participants were blinded to their measurements. Differential …