MANILA — The Department of Health on Friday said that the Philippines will only use antigen tests that are most accurate at detecting COVID-19.

An antigen test, another type of test used to diagnose COVID-19, measures a portion of the SARS-CoV-2 virus using swab samples, similar to the gold-standard polymerase chain reaction (PCR) test.

While it is not as accurate as a PCR test, it is said to be better at testing patients than rapid antibody test kits. Antigen tests can also process results as fast as 15 minutes.

“Ang diagnostic performance ng antigen test kit dapat 80% sensitive and 95% or more specific,” Health Undersecretary Maria Rosario Vergeire said during a virtual briefing.

(The diagnostic performance of the antigen test kit should be 80% sensitive and 95% or more specific.)

Sensitivity refers to a test’s ability to detect SARS-CoV-2 -- or the true positive rate -- while specificity refers to the test’s ability to identify those without the virus or the true negative rate. High sensitivity and specificity rates will ensure that the test won’t result in too many false positives and false negatives.

OMNIBUS GUIDELIENS

Vergeire said the protocols for antigen testing is just one of the things being finalized for the government’s omnibus guidelines meant to be released next week. She said the guidelines will also include protocols for surveillance, contact tracing and isolation.

“Lahat ng yan pinagtrabahuhan namin, sinubmit sa IATF last Monday. There were comments and we are now trying to finalize together with the other agencies para hopefully next week makapagpalabas tayo,” Vergeire said, adding that the department will have to make another presentation before the guidelines are released.

(All of that we’re working on and we submitted to the IATF last Monday. There were comments and we are now trying to finalize together with the other agencies so hopefully next week we can release it.)

National testing czar Vince Dizon earlier said that the government is studying the possibility of using antigen tests to screen local travelers and returning Filipinos.

Vergeire said the omnibus guidelines will be including testing protocols for all types of COVID-19 tests for special groups, such as returning Filipinos, locally stranded individuals, international and domestic tourists and workers.

TARGETED TESTING

However, she said, antigen testing “cannot be used for indiscriminate testing. It can only be used for targeted testing.”

Of the 8 antigen test kits registered with the Food and Drug Administration, two have already been validated with the Research Institute for Tropical Medicine. However, the results have not yet been released, Vergeire said.

On Thursday, clinical epidemiologist Dr. Leonila Dans of the University of the Philippine College of Medicine shared with ABS-CBN News a study she did with fellow doctors. The study reviewed 9 research papers on the use of antigen testing for COVID-19.

Asked if antigen testing can indeed be used on travelers who do not show any signs of illness, she said: “Ang baba ng accuracy. Nakita namin 20% lang ng mga may COVID ang made-detect ng iyong antigen test. So marami tayong mami-miss, 80% mami-miss natin.”

(The accuracy is low. We saw that only 20% of those with COVID can be detected by the antigen test. So it can miss 80% of people with COVID.)

She said the danger there is that people will have a false sense of security if they test negative.

Dans said that only 2 studies ran tackled the use of antigen tests on asymptomatic individuals and that there really is a need for more studies.

Their review also showed that different kinds of antigen tests resulted in different levels of sensitivity, ranging from as low as 0% to as high as 94%.

She said antigen tests are more appropriate for symptomatic patients who need quick test results.

But overall, they recommended that more time is allotted to study antigen testing. This aligns with the World Health Organization recommendation for more research.