Rapid Diagnosis of COVID-19 by Chemical Analysis of Exhaled Air

Overview

Since the start of 2020, the new SARS-CoV-2 coronavirus is causing a real global health crisis. In France, nasopharyngeal swabs are used to obtain the sample needed for respiratory infection screening. There are three major difficulties with this type of sampling: I) It is really unpleasant for the patient because the device has to be pushed into the nostril to reach the nasopharynx. It causes some patients to bleed or even feel uncomfortable. II) It is not easily accepted by children. III) It is dependent on the availability of swabs. Faced with these difficulties linked to the initial sampling, new methods are being studied to enable a rapid and non-invasive diagnosis of COVID-19 based on the instantaneous identification of metabolites or volatile organic compounds (VOCs). Due to their sensitivity and the wealth of information that can be provided, the most promising techniques are based on mass spectrometry coupled with a soft ionisation system. For example, on-line exhaled air analysis is capable of detecting a very large number of VOCs. Various tests on metabolites in the exhaled air have already been carried out without being totally conclusive because the existing instruments suffer from various limitations: I) poor repeatability/accuracy in the chemical characterisation of exhaled air ; II) too high specificity (detection of only part of the emitted compounds); III) too limited sensitivity; IV) and poor adaptation to be deployed in a clinic. In order to overcome these various limitations, we propose the use of a new generation of mass spectrometer: Vocus PTR-TOF. The Vocus PTR-TOF is a Proton Transfer Mass Spectrometer (PTR-MS) developed for the detection, in real time, of trace VOCs in industrial environments, laboratories or directly in the environment. This new generation of instrument offers the following advantages: I) unequalled sensitivity : II) a robust ionisation system not affected by environmental conditions (relative humidity...) ; III) a high mass resolution allowing precise identification of compounds ; IV) a compact and durable architecture allowing deployment in a constrained environment such as hospital, airport… The sensitivity and speed of measurement allow the expiration process to be monitored in real time, bringing an additional dimension to the measurement and the chances of success.