Disease detection by infrared goes viral


A fast and simple technique to detect viral infections in blood could become a new front-line tool to tackle the spread of deadly diseases

Roy, S., Perez-Guaita, D., Bowden, S., Heraud, P., Wood, B. R.: “Spectroscopy goes Viral: Diagnosis of hepatitis B and C virus infection from human sera using ATR-FTIR spectroscopy,” Clinical Spectroscopy (2020)

A new method to detect viruses in the blood could make diagnosis of infections easier, faster and less expensive. Researchers at Monash University and the Victorian Infectious Diseases Reference Laboratory, in Australia, describe the development of an infrared based technique to detect Hepatitis B and Hepatitis C infection in the journal Clinical Spectroscopy.

“Viral hepatitis is a leading cause of death and disability worldwide, responsible for approximately 1.45 million deaths each year,” says Bayden Wood of the research team at the Monash Centre for Biospectroscopy. He explains that the most reliable current methods of diagnosis require bulky equipment, are expensive and time consuming. Alternative rapid diagnostic tests are available, but they have incomplete sensitivity, they don’t provide quantitative information on the level of infection and their refrigeration requirements make them difficult to use in remote environments. Wood emphasizes that there is a definite need for better methods.

Applying a blood sample for analysis by ATR-FTIR
Applying a blood sample for analysis by ATR-FTIR. Credit: Bayden Wood

“Our test uses portable technology and doesn’t require special conditions or chemicals,” says Wood. He therefore feels it could have significant social and economic benefits in diagnosing infections at point-of-care.

“Our paper also comes at an interesting time given the rapid spread of a novel coronavirus,” Wood points out. “New techniques that can analyse blood at point-of-care without expensive consumables could help fight the spread of that disease.”

The test re-purposes, for the detection of viruses, an analytical technique called Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR). This is based on the absorbance of infrared radiation by the molecules in a sample. The researchers were stimulated to explore applying ATR-FTIR to viruses after successfully using it for diagnosing malaria, a non-viral disease caused by a single-celled parasite.

The detection process begins by spinning a sample of blood in a small benchtop centrifuge to separate the molecules in the blood by size. A tiny five microlitre sample of the fraction containing the largest molecules, including large proteins, is then applied directly into the ATR-FTIR equipment and quickly dried before the analysis recording. The results then come through in about 20 seconds.

These results, known as an IR absorption spectrum, display the intensity of infrared absorption across the different frequencies of infrared light. Fortunately, distinct bands of absorption could be detected due to some of the viral proteins and also some of the antibody proteins produced by the immune response to the viruses. A complex software algorithm helps pick out these tell-tale bands from all the other signals.

The test is already significantly sensitive and specific, but Wood accepts that it would benefit if these aspects could be further improved. The researchers are now tackling that challenge. They also hope to widen their research to apply the technique for detecting other viral infections. This will hopefully also allow detecting mixed infections, as tests to date have mainly focused on blood infected with a single virus.