February 3, 2023

The Department of Health-Cordillera has reiterated its advice against the use of the rapid antigen test kits for mass testing to detect Covid-19.

DOH-Cordillera Asst. Director Amelita Pangilinan said last week the agency’s Health Technology Assessment Council (HTAC) does not recommend rapid antigen test kits for indiscriminate use, especially in testing individuals who do not show symptoms of the Covid-19.

Pangilinan said the HTAC does not also recommend the rapid antigen test kits for returning overseas Filipino workers, locally stranded individuals, and tourists. Results of antigen test should not also be used as a clearance for employees who are returning to work.

“The Reverse Transcription-Polymerase Chain Reaction (RT-PCR) remains the gold standard for the diagnosis of Covid-19,” Pangilinan told members of the city council who invited her and City Health Services Office (CHSO)-Infectious Disease Division Head Donnabel Panes on Oct. 5 to clarify issues regarding the use of the rapid antigen test.

Pangilinan said the rapid antigen test kits, which produce results in as fast as 15 to 45 minutes and within one to three hours, are used only for targeted screening, such as in hospitals or for individuals who were exposed to positive cases and are manifesting the Covid-19 symptoms.

“The rapid antigen test is only for targeted screening, such as (among) patients in hospitals where turnaround time is critical to minimize transmission to healthcare providers and to other patients. Those who are not showing any symptoms of the Covid-19 and have no exposure to positive cases should not be tested using the rapid antigen test kits,” she said, quoting the recommendation from the HTAC.

To recall, the city government has started using the rapid antigen test for close contacts of positive cases and for domestic tourists and visitors with essential travel, based on a resolution from the Inter-Agency Task Force for Emerging Infectious Diseases.

Pangilinan said rapid antigen tests are used to identify current acute or early infection, which is why it has been found useful when the viral load is high, usually within five days when the symptoms manifested.

“The antigen test is a type of rapid diagnostic test that detects the presence of viral proteins expressed by the virus that causes the Covid-19. The antigen is expressed only when the virus is actively replicating, this is why the rapid antigen test is most useful when the patient is manifesting symptoms.”

Panes, meanwhile, said they are wrapping up the comparative study that the CHSO conducted for the rapid antigen test and the RT-PCR test, of which results for the 799 out of the 869 individuals enrolled for the study are already out.

She said from the tests conducted among the 799 close contacts of Covid-19 patients, 77 had positive results using the rapid antigen kits or a positivity rate of 10 percent while 117 had positive results using the RT-PCR or a positivity rate of 15 percent.

The antigen brand being used in Baguio is the SD Biosensor, which was donated by the Korea Trade Investment Promotion Agency.

Panes said in terms of the positivity rate or the percentage of true positive results, the brand registered 62 percent, which is below the World Health Organization standard of 80 percent or higher. In terms of specificity or the percentage of true negative results, the brand registered 99 percent, which is higher than the 95 percent standard of the WHO. – Jane B. Cadalig