PARIS – Soon, a machine, as quick and simple as a breathalyzer, could be used to detect COVID-19 from molecules present in exhaled air. The research team from Institut de recherches sur la catalyse et l’environnement de Lyon (IRCELYON – Lyon Institute for Research on Catalysis and the Environment) is investigating the analysis of volatile organic compounds (VOCs) found in exhaled breath for COVID-19 detection.
“We have applied our expertise in atmospheric chemistry and air quality to test this new protocol, which detects the COVID-19 virus by analyzing the air exhaled by the patient,” Christian George, deputy director of IRCELYON, told BioWorld.
Similar principle to the breathalyzer test
IRCELYON is a joint research project between French National Centre for Scientific Research and Claude Bernard University in Lyon, which specializes in atmospheric and environmental physical chemistry. For years, his team has been developing new techniques for measuring air “with reproducible quantification of ultra-fine particles ranging in size from micrometers to nanometers,” said George.
The idea is hardly new: in 1954, the breathalyzer enabled analysis of blood alcohol levels. Since then, researchers have discovered that exhaled air contains thousands of molecules produced by our metabolism, in a composition that varies according to our state of health. During an infection, our cells are controlled by the virus and produce viral proteins, to the detriment of most of their normal activities. As a result, the particles that an infected individual expels from their lungs can differ from those of a healthy subject.
The analysis of VOCs in human breath has been the subject of many research studies. However, most have come across the same obstacle: the volatile molecules that could serve as markers for a disease have always been present in concentrations that are far too low, typically in the range of parts-per-trillion to parts-per-billion. “Worse still, as a humid and hot environment, exhaled air does not lend itself to measurement, and challenges the reliability of the results,” said George. The approach is promising on paper, but in practice its applications have been a long time coming.
IRCELYON's team of physicochemists joined forces with two other research teams, as well as infectious disease specialists and intensive care teams from a Lyon hospital. Thus, the center for research in infectious diseases (CIRI) at INSERM in Lyon, and the intensive care unit and infection disease unit at the Croix-Rousse hospital have been supplying clinical data specific to COVID-19 and working on the clinical side of the breath test for the COVID-19 project.
The statistical model behind the new diagnostic technique was studied by the Institute of Analytical Sciences (ISA) in Lyon, one of the largest European research centers specializing in theoretical chemistry, modeling, biochemistry, analytical chemistry and physics. The Lyon research project was financially supported through funding provided by the Region Auvergne Rhône-Alpes, the French government and the European Regional Development Fund (ERDF).
A new generation of mass spectrometers for VOC
Swiss firm Tofwerk AG supplied the cutting-edge mass spectrometer specially designed for this research project. Tofwerk recently launched the Vocus PTR-TOF, a new generation of proton-transfer-reaction mass spectrometers for sensitive, real-time detection of VOCs in industry and the laboratory. “Our instruments are normally used in atmospheric science to analyze clean air. Vocus PTR-TOF is being tried out in a variety of applications, ranging from detecting oil rig emissions to identifying fentanyl in lab samples,” Marc Gonin, CEO of Tofwerk told BioWorld.
Tofwerk’s Vocus PTR-TOF is a sensitive, online VOC analyzer that can simultaneously detect hundreds of volatile chemicals at parts-per-trillion levels. Gaseous samples are analyzed directly, without any preparation required, and results are reported in real time at extremely high rates. For breath analysis, the Vocus PTR-TOF is equipped with a heated breath inlet with disposable non-rebreathing mouthpiece, to avoid the risk of disease transmission between potentially infectious patients. This portable system, about the size of a domestic refrigerator, weighs 350 pounds and can be installed almost anywhere, including clinical examination rooms or screening checkpoints.
“This new device from Tofwerk met our specifications,” said George: ultra-low detection thresholds, with a sensitivity level of one part per quadrillion (1 ppq: 10-12), compared with an average sensitivity for other technology of one part per billion (1 ppq: 10-9). Furthermore, VOC measurements are not affected by the relative humidity of the sample. The mass resolution power up to 15,000 enables identification of isobaric compounds in complex compounds, and the system has a user-friendly data acquisition interface and post processing graphics software for analyzing high-resolution data.
Clinical trial to identify the VOC signature of COVID-19
For the past five months, the Lyon research consortium has been testing the device in the intensive care and the infectious disease units at the Croix-Rousse hospital. “When a person exhales into the device, we record the chemical composition of the exhaled air,” said George, adding that each exhalation contains 30,000 pieces of information per second. His team performed statistical processing with ISA researchers to find out what information differentiates people with COVID-19 from healthy ones. The first calculations showed that they can indeed distinguish infected people from healthy ones.
The device is entering a phase II trial after three months of being used on dozens of people, among whom some 20 had the virus and the others did not. “It is about identifying the signature of COVID-19 in the patient's breath, i.e., the thousands of VOCs specific to COVID-19 among the 30,000 bits of information measured in the patient's exhaled air each second,” said George.
Data collected at the hospital is undergoing rigorous mathematical analysis, led by ISA, to identify potential molecular biomarkers of COVID-19. “The first results show that we are on the right track. However, we remain cautious because our objective is to present precise and reproducible results by the end of the year,” said George. According to Jean-Christophe Richard, head of intensive care at the Croix-Rousse hospital, “this type of rapid test means we can get the results right away and move patients to the right part of the hospital. As we have several effective treatments, the quicker we can diagnose, the quicker we can treat them”.
The ability to quantify hundreds of trace VOCs simultaneously opens the door to powerful breath fingerprinting, whereby COVID-19 or other infections, such as Legionnaires’ disease or cancer, could be detected based on unique metabolic and VOC markers. In contrast to swab-based COVID diagnostic methods that take from minutes to hours per sample to collect and analyze, the real-time nature of the Vocus PTR-TOF suggests the potential to screen one or more people every minute. The question is going to be, how to make this technology smaller and less expensive. This new equipment costs $460,000.