NEW YORK ─ Researchers at the QIMR Berghofer Medical Research Institute in Brisbane, Australia, have developed a proof-of-concept instrument that leverages spectroscopy to screen for SARS-CoV-2 and potentially identify people who could become sicker from the infection.
The diagnostic testing platform, based on attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, has shown promise in recent studies and could enable SARS-CoV-2 tests that provider faster results than RT-PCR and higher sensitivity than antigen testing, said Michelle Hill, an associate professor at QIMR who is leading the test's development.
Though ATR-FTIR spectroscopy is broadly used to provide detailed information on the composition of solid, liquid, and gaseous samples for pharmaceutical, materials science, and life sciences applications, the technique is not currently applied for commercial in vitro diagnostic testing.
Nonetheless, researchers are exploring its potential for testing related to numerous diseases because of its ability to provide a chemical snapshot of a patient sample by measuring the vibration of chemical bonds and obtaining spectral signatures that correlate with illness.
"The simplicity of FTIR spectroscopy and rapid time to result makes [it] attractive for diagnostic and screening applications," Hill said.
She and her colleagues recently published the results of a study in Biomedicines that described the development and evaluation of a proof-of-concept ATR-FTIR screening test with a sensitivity of 93.5 percent for the detection of SARS-CoV-2 in patient saliva.
The investigators leveraged three biological systems — cultured cells infected with SARS-CoV-2; a mouse model of SARS-CoV-2 infection; and a patient cohort involving 60 COVID-19 patients and 44 healthy control subjects — to determine the pathophysiological response to SARS-CoV-2 infection detected by the infrared spectroscope.
The group used the ATR-FTIR spectrometer to obtain spectra of absorption or emission from saliva samples by applying infrared radiation and measuring the frequencies at which radiation is absorbed. The attenuated total reflectance mode of sampling combined with a sample decontamination procedure enabled spectra acquisition at a rate less than two minutes per sample.
The cell and mouse infection models used ultraviolet-inactivated virus in control infections, allowing a clearer distinction between active infection and general stress response, Hill said, adding that while the cell and mouse systems modeled severe infections, the COVID-19 patients were recovering from the infection.
The group used the human cohort data to develop a COVID-19 saliva FTIR signature and found that individuals who were recovering from the SARS-CoV-2 infection had a slightly different signature from those who had active disease, Hill said.
To determine the robustness of the signature, the group compared the COVID-19 signatures from the three biological systems with signatures obtained from three other studies that used FTIR for COVID-19 saliva analysis and "observed overlap in the identified spectral signatures across the different systems and studies," Hill said.
The current research builds on a study published last July in Analytical Chemistry in which the QIMR group with colleagues at Indian Institute of Technology in Mumbai described the development and evaluation of a blood-based ATR-FTIR spectroscopy test as a COVID-19 severity tool to facilitate COVID-19 patient management.
Leveraging blood samples from 160 COVID-19 patients, the study investigators found differences in the infrared spectra in the patients who became severely unwell compared to those who had less severe symptoms, Hill said.
The investigators tested the algorithm on blood samples from a separate group of 30 COVID-19 patients and found it was 85 per cent accurate in predicting which patients would become severely ill.
As a result of the studies, the QIMR group has its eye on developing a commercial version of the ATR-FTIR testing platform. That would require further development and validation in larger prospective patient studies, Hill said, adding that if such a test can be commercialized, it could include separate spectroscopy signatures for screening and disease severity.
Though the current prototype requires manual pipetting of saliva samples and inactivation of the virus using ethanol in the lab, a commercial platform would integrate those steps within one testing platform, Hill said.
To make the system more applicable to clinical diagnostic testing, the developers would need to develop a saliva receptacle that can be connected to the spectrometer, she added.
The group is seeking funding to make additional changes to the test and move it closer to commercialization, Hill said, adding that they are discussing the potential for its further development with in vitro diagnostic test manufacturers.
A commercial version of the platform would consist of the saliva receptacle, a laptop, and a benchtop Agilent Cary 630 FTIR spectrometer, the model used in the Biomedicines study.
The spectrometer is amenable to point-of-care testing, Hill said, adding that in a commercial screening application, it could be used to determine the risk of SARS-CoV-2 infection in five minutes, making such a test useful for office-based testing and for entertainment venues.
The COVID-19 severity signature could be used in hospitals to quickly identify patients with potential for severe illness, she said.
Additionally, individuals at home who are concerned about whether they could develop a severe form of COVID-19 could send saliva samples to a central laboratory for testing, using saliva collection kits provided by the test developer, Hill said. The laboratory would run the FTIR COVID-19 severity test and return results electronically to the patients or their physicians. That reduces the potential for onward transmission of the virus, Hill noted, because a patient who tests positive would remain at home while testing is completed. If the test indicates that the infection is not likely to be severe, the patient could decide to quarantine at home for the duration of the infection.
Seeing the potential of FTIR for diagnostics, other organizations are also developing testing platforms. Georgia State University researchers are developing an infrared spectroscopy method that could help clinicians avoid tissue biopsies in detecting lymphoma, subcutaneous melanoma, or colitis. Researchers at Germany's Ruhr University Bochum have developed an automated pathology tool based on Fourier transform infrared imaging, and UK-based ClinSpec Diagnostics is developing an infrared spectroscopy-based test for diagnosing brain cancer patients at an early stage.
FTIR is also getting more recognition for its potential for use in SARS-CoV-2 testing, according to Hill. A few research groups have recently used FTIR spectra collected from the saliva of COVID-19 patients and healthy controls to develop prediction algorithms that demonstrated high predictive accuracy, she said.
In one such study published last October in Scientific Reports, investigators at the Secretaría de la Defensa Nacional in Mexico City described the development of salivary vibrational modes analyzed by ATR-FTIR spectroscopy to detect COVID-19 biological fingerprints that allow patients infected with SARS-CoV-2 to be differentiated from healthy patients.