Exhaled Breath Aerosol for the Etiological Diagnosis of Respiratory Tract Infections: a Pilot Study

Respiratory infections have a significant impact in terms of morbidity and mortality, both in the EU and globally and were responsible for the majority of pandemics in the last centuries. Human breath is an attractive sample type, given the ease of sample collection via non-invasive methods, its direct link to the route of transmission, and its potential role as an indicator of infectiousness. In particular, recent studies have focused on the exhaled breath aerosols (XBAs). Aerosol transmission was demonstrated for many respiratory infections, including pandemic influenza, respiratory syncytial virus (RSV), tuberculosis (TB) and COVID-19. Pathogen detection in XBA samples has shown a good sensitivity, but currently available research tools are highly technical and resource demanding. New and simplified XBA collection devices (Face masks, AveloCollect Blow tube device) are currently under evaluation, and further clinical studies are needed in order to assess their feasibility for pathogen detection in clinical practice, especially for etiological diagnosis in patients with unspecific respiratory symptoms.

The objective of this study is to evaluate the feasibility of XBAs collection and analysis (index test) using the molecular tests currently in use at San Raffaele Hospital for the detection of respiratory pathogens in clinical samples, compared to upper respiratory secretion and sputum samples, that will be collected using standard procedures and analysed using the same kits (comparator tests).

Inclusion criteria

• Adult age (≥18 years)
• Subjects with one or more symptoms of respiratory tract infection (fever, cough, sore throat, dyspnea, conjunctivitis and/or rhinitis).
• Samples collected within 3 days from symptom onset.
• No antibiotic drug taken during the previous 3 days

Exclusion criteria

• Pregnancy
• Samples collected after 3 days from symptom onset.
• Antibiotic drug taken during the previous 3 days