Infectious disease specialist: Don't take antigen results as gospel

The Caribbean Public Health Agency (CARPHA) has authorised US-based company Sensiva Health’s C19 covid19 diagnostic test. This is a form of PCR (Polymerase chain reaction) testing.

In a release, the company said the new test is “one of the first to receive authorisation” by CARPHA.

It said the test is a “gold standard real-time multi-method collection test with 100 per cent specificity and sensitivity, offering next-day risk of exposure information.

“Sensiva can provide Caribbean healthcare providers with risk exposure information and guidance immediately after results are received via an online report, or by phone through Sensiva’s proprietary mobile application. While both clearly explain the test results, a team of telemedicine professionals will also be available to answer questions via live chat, e-mail, or phone support

“Based on the most powerful technique and tool in molecular biology, PCR has proven to be the most reliable covid19 testing method. Using enzymes sourced from heat-stable bacteria to replicate DNA/RNA, Sensiva utilises the latest technology platforms to perform this highly specific and reliable process, which results in rapid and highly accurate reproduction of DNA/RNA molecules in its laboratory.”

Infectious disease specialist Dr Rajeev Fernando told Newsday he did not believe “anything in medicine is 100 per cent,” instead ranking the test as having 99 per cent sensitivity and specificity.”

Dr Fernando – also vice president of clinical affairs at Sensiva Health travelled to Wuhan, China, in January when there were only 50 covid19 cases being reported globally.

He has also treated and tested patients during multiple infectious disease outbreaks, including Ebola virus in Sierra Leone; Zika virus in Brazil; tropical disease in Sudan; as well as providing medical services for Tsunami Relief in India.

He explained the concepts of specific and sensitive testing, saying “Sensitivity – you want to pick up everything, if there’s any chance this patient has covid19, you want to pick it up for sure. Even if there’s a 0.1 per cent chance you want to make sure that’s found.

“Once you have established this, you tell the patient you did the sensitive test which is positive. But it’s a wide, wide array, so other things can be causing it. There are seven different coronaviruses. SARS-Cov back in 2003, now we have SARS Cov-2 which causes covid19, MERS (Middle East respiratory syndrome-related coronavirus)…It could be any of the coronaviruses. The specific test now is to wipe out all the nonsense and identify covid19 itself.”

He said antigen (rapid) tests lack sensitivity and are not as reliable. Because of this, he warned, its results should not always be taken as gospel.

“It’s one thing to have false positive, but false negative – that’s when you’re failing the patient. At the height of the breakout, I didn’t believe any result. I looked at the patients and told them, this result is negative but I’m still going to treat you because you have all the symptoms.

“Some physicians are so fixated on negative (antigen) test results. They just tell the patient, ‘Well, you’re negative,’ and they are allowed to go back into the community and spread (the virus) more. We’ve seen cases like this where a few days later, the patient comes back with bad pneumonia and they die from the virus.”

He said he has been monitoring the spread of the virus throughout the Caribbean region, adding that TT’s current situation is “certainly concerning and very worrisome.”