What Are The Different Types Of Coronavirus Tests?
The antigen test can rapidly detect fragments of virus proteins in samples collected from swabs swiped inside the nasal cavity. It can diagnose active infection by detecting the earliest toxic traces of the coronavirus rather than the virus itself.
There are three broad categories of tests being introduced worldwide amid the coronavirus disease 2019 pandemic. Two tests diagnose whether you have an active infection, and a third indicates if you previously had the virus.
Here’s how they work:
Most tests look for bits of the virus’ genetic material, and require a nasal swab that is taken by a health professional and then sent to a laboratory. This is considered the most accurate way to diagnose an infection, but it’s not perfect: the swab has to get a good enough sample so any virus can be detected.
These tests usually take hours to process at the laboratory so you likely won’t get results back for at least a day, though a handful of rapid tests take about 15 minutes on site. Other genetic tests use saliva, instead of a swab.
A newer type of test looks for proteins found on the surface of the coronavirus, rather than the virus itself. These antigen tests are just hitting the market, and experts hope they’ll help expand testing and speed up results.
Antigen tests aren’t as accurate as genetic tests, but are cheaper, faster and require less specialized laboratory equipment. They still require a nasal swab by a health professional.
A recently approved test from Abbott Laboratories takes 15 minutes and can be performed at schools, offices and other locations.
Antibody tests look for proteins that the body makes to fight off infections in a patient’s blood sample. Antibodies are a sign that a person previously had COVID-19.
Scientists don’t yet know if antibodies protect people from another infection, or how long that protection might last. So antibody tests are mostly useful for researchers measuring what portion of the population was infected.
In the Philippines, health experts are reviewing the omnibus guidelines of the Inter-Agency Task Force (IATF) for the Management of Emerging Infectious Diseases on the use of rapid antigen test to detect COVID-19 following the recommendations issued by the World Health Organization (WHO).
In a press briefing, Health Undersecretary Maria Rosario Vergeire said on Monday, Sept. 14, that the Health Technology Assessment Council (HTEC) will have to revise the guidelines on antigen test to make sure that the IATF’s rules on the use of test methods are aligned with the WHO recommendations.
“We met a bottleneck over the weekend when WHO issued their new recommendations on rapid antigen tests. Because of this new evidence, the HTEC will have to revise the guidelines,” Vergeire disclosed, referring to the WHO’s interim guidance on antigen-detection in the diagnosis of SARS-CoV-2 infection using rapid immunoassays dated Sept. 11.
SARS-CoV-2 is Severe Acute Respiratory Syndrome coronavirus 2, the virus that causes COVID-19.
The IATF is expected to come up with the guidelines detailing the appropriate use of COVID -19 test methods that are available in the country. Aside from the antigen test, the guidelines will cover rapid antibody test kits or RATs and real-time reverse transcription-polymerase chain reaction (rRT-PCR) tests.
Based on IATF Resolution No. 96 dated Sept. 7, the rRT-PCR test remains the gold standard for confirmatory testing for COVID-19.
On Sept. 8, Malacañang – through presidential spokesman Harry Roque – announced that the antigen test may be used as a pre-boarding requirement for asymptomatic domestic tourists before departure and travel to destinations or as a requirement upon entry at the place of destination if in accordance with the protocols of the local government unit.
It may also be used in the testing of domestic tourists who turn symptomatic at the place of destination, if there is no rRT-PCR capacity, Roque said.
But according to Vergeire, the WHO’s position that the antigen test “is not advisable to use in borders for screening will have an impact in the guidelines” being formulated by the government.
“We see changes every day because this is an evolving situation. It’s very dynamic because of all these new evidences that are coming out everyday,” she said. “By early next week, we can issue the omnibus guidelines.”
Last month, Vergeire said there were draft guidelines that would be submitted to experts for their opinions.
“The objective of omnibus guidelines is for us to be able to put in one document all of these available testing methodologies in the country for COVID-19,” she pointed out. “The guidelines will show how and when the test kits must be used.”
According to Vergeire, the country started with rRT-PCR and then came the RATs and the antigen testing.
Vergeire said other innovations would come out in the coming weeks or months so the government must prevent having misleading information and make sure that the general public and health facilities are guided on the tests they are supposed to use.
She pointed out that RATs, for instance, does not detect the virus but merely antibodies that come out only after five to seven days from infection.
On the other hand, two days prior to the illness, rRT-PCR can already detect the virus.
“It is very sensitive. Even if you have completed your 14 days (quarantine), even if it’s already one month, the test can still detect the virus,” Vergeire explained.
She said the antigen test, which is more sensitive and accurate than RATs, is appropriate to use during the first five days of the illness.
But it cannot be used if a person is “pre-symptomatic” or having symptoms beyond six to seven days of illness. “It will turn negative,” she said.
“Hopefully, the omnibus guidelines will guide all of our implementers, the general public. They would know which test to use and in what stage of their illness. It will provide us with harmonized guidelines,” Vergeire said.
After the experts have given their opinions, the document will be referred to the COVID-19 Laboratory Expert Panel that will give the final comments. It will then be submitted to the Department of Health’s Executive Committee and the IATF.