RT-PCR test is ‘gold standard’ for Covid-19 detection – De Gascun

The real-time reverse transcription polymerase chain reaction (RT-PCR) test currently in use in Ireland to detect Covid-19 in patients is the ‘gold standard’, the Director of the National Virus Reference Laboratory at University College Dublin has said.

According to Consultant Virologist Dr Cillian De Gascun, unverified claims suggesting the test had a sensitivity or detection rating of between 30 and 70 per cent were inaccurate.

“This arbitrary notion that it [test] is between 35 and 70 per cent … in essence, it’s irresponsible,” Dr De Gascun told the Medical Independent. 

The test used to detect the novel coronavirus was “incredibly sensitive” and effective, he outlined.

“It is capable of detecting fewer than 10 copies of a particular pathogen in one millilitre of fluid. This is the same technology we use to monitor people with HIV infection, or hepatitis C infection, the same technology we use to diagnose influenza.”

It was unclear how concerns about the test had arisen, said Dr De Gascun. However, he suggested a number of reasons why the claims had been given credence, even among healthcare professionals.

Firstly, the unprecedented public health emergency has meant that testing for all ‘colds’ and influenza viruses in hospitals had ceased, as tests are reserved for suspected Covid-19 patients, explained Dr De Gascun.

“We are not testing for the normal respiratory viruses that are circulating at this time of the year. People get symptoms and they assume they have Covid-19. They get a negative test and then they say ‘oh, the test is wrong, I’m sick’. We’re not saying you’re not sick. What we’re saying is that you don’t have Covid-19.”

Secondly, a high test sample quality is required to detect the virus on review in the laboratory, outlined Dr De Gascun. If a “proper sample” is provided the sensitivity is very high.

HIQA recently published a rapid health technology assessment of alternative diagnostic testing methods for detecting Covid-19. Real-time RT-PCR remains the ‘gold standard’ test for detecting and confirming cases, according to HIQA.