The Evaluation of FeNO for Predicting Response to ICS in Subjects With Non-specific Respiratory Symptoms

Randomised, double-blind, placebo-controlled trial with planned enrolment of 264 patients from the UK and Singapore. Eligible patients are 18-80 years old with ≥6 weeks' duration of non-specific respiratory symptoms defined as cough and/or wheeze and/or dyspnoea. Patients with FEV1 \<90% predicted at visit 1 must show reversibility of \<20% at visit 1 or within the prior year. Key exclusion criteria are prior diagnosis of asthma; evidence of concomitant chronic respiratory disease, respiratory tract infection; or known significant risk factor for cough or wheeze. Baseline assessments will include spirometry (FEV1, forced vital capacity) and FeNO measurement. Patients will be provided with a peak flow meter for twice daily measurement throughout the study. At 2 weeks, a clinical assessment and spirometry will be performed to confirm eligibility, and patients will complete four validated questionnaires to assess quality of life, asthma control, and asthma symptoms, including a visual analog scale for bother from asthma symptoms. Eligible patients will then be stratified by baseline FeNO level (normal ≤25, intermediate \>25 to ≤50, or high \>50 ppb); each group will be randomised to receive beclometasone 400 mcg daily or placebo for 6 weeks. An optional blood sample will be collected from consenting patients to assess blood eosinophils. At visit 3, final assessments will include spirometry, FeNO measurement, and all questionnaires. Interaction analysis will be used to determine whether a differential effect exists in response to ICS between FeNO groups.