Point-of-care testing – in other words, testing patients as soon as they arrive at the hospital – is essential for enabling healthcare workers to rapidly diagnose patients and direct those who test positive for infection to dedicated wards. A recent study showed that SAMBA II, a new point-of-care PCR test for SARS-CoV-2 developed by Cambridge researchers, was able to dramatically reduce time spent on COVID-19 ‘holding’ wards – allowing patients to be treated or discharged far quicker than with current lab testing set-ups.
PCR tests involve extracting a miniscule amount of RNA from the virus and copying it millions of times, creating an amount large enough to confirm presence of the virus. The virus is captured through a swab inside the nostrils and at the back of the throat. However, it can take as long as 14 days for an individual to show symptoms of COVID-19, by which time the virus may have moved away from the nose and throat and into the lungs and other tissues and organs, making it harder to detect via a swab test. As a result, studies have shown that PCR tests can miss as many as a half of infected patients five days after infection.
Antibody tests provide an alternative way of identifying infected individuals, but antibodies – molecules produced by our immune system in response to infection – generally do not appear until at least six days after infection.
Professor Ravi Gupta from the Cambridge Institute of Therapeutic Immunology and Infectious Disease at the University of Cambridge said: “We still do not have a gold standard test for diagnosing COVID-19. This poses a challenge to healthcare workers who need to make quick and safe decisions about how and where to treat patients.
“The two main types of test – PCR and antibody tests – both have limitations because of the nature of coronavirus infection and how our body responds. But we’ve shown that if you combine them and carry out both at point of care, their reliability can be hugely increased.”
Professor Gupta led a team that used the approach of combining rapid point-of-care PCR and antibody tests to diagnose 45 patients at Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust. The results of this peer-reviewed study are published in Cell Reports Medicine.
Image: Man taking COVID-19 test
Credit: U.S. Pacific Fleet
Reproduced courtesy of the University of Cambridge