Red Cross saliva test accurate as RT-PCR

By Joseph B.A. Marzan

The Philippine Red Cross (PRC) Iloilo Chapter on Friday encouraged more people to get themselves checked for the coronavirus disease 2019 (COVID-19) via saliva-based testing.

As of this time, the PRC is the only entity allowed by the Department of Health (DOH) and the Research Institute for Tropical Medicine (RITM) to conduct saliva based COVID testing, according to PRC Iloilo Chapter Administrator Gilbert Paul Valderrama.

Drool specimens are collected from patients and tested via Reverse Transcription-Polymerase Chain Reaction (RT-PCR) machine at the PRC Iloilo Molecular Laboratory in Passi City.

RT-PCR testing is the gold standard in detecting COVID-19 since the pandemic broke out in mid-March of 2020.

Until the approval of saliva-based test, the common way of extracting specimen is via swabs inserted and retracted from either the nose or the throat, or even both, to collect samples of ribonucleic acid (RNA) of the SARS-CoV-2, the virus which causes COVID-19.

The concept of saliva-based RT-PCR testing, which bypassed the usual RNA collection method, was first introduced by researchers at the University of Illinois in Urbana-Champaign in June 2020, led by Filipno scientist Diana Rose Ranoa of the university’s Department of Chemistry.

The study suggested that the saliva-based process was “operationally simple, utilizes readily available materials, and can be easily implemented by existing testing sites, thus allowing for high-throughput, rapid, and repeat testing of large populations.”

President Rodrigo Duterte publicly backed saliva-based testing as early as January of this year, but the DOH only issued guidelines for testing on April 6 via Department Memorandum (DM) No. 2021-0161.

The DM stated that only licensed COVID-19 laboratories certified by the RITM are allowed to perform saliva-based RT-PCR tests, with point-of-care clinics, specimen collecting facilities, and disease reporting units allowed to perform specimen collection provided that authorized laboratories provide training to these facilities.

Recent case bulletins by the DOH-Western Visayas Center for Health Development (DOH-WV CHD) indicated that the current COVID case numbers, including the grand total number of confirmed cases, as well as numbers of active cases and recoveries, included the PRC’s saliva-based tests.

The DOH-WV CHD rules cited an unnumbered memorandum dated June 14, 2021, which cannot be found on the websites of either the central or regional DOH offices.

Instead, the latest issuance of the DOH on the matter, Department Circular No. 2021-0275 dated June 28, 2021, reiterated that the nose- or throat-based swabs remained the ideal way of collecting specimen

Valderrama told Daily Guardian on Air that they have already conducted around 2,000 to 3,000 saliva-based tests from Iloilo City alone since they started collecting saliva specimen in March of this year.

Specimens are collected by the PRC through its satellite partner collection centers at the St. Paul’s Hospital and Iloilo Doctors Hospital in Iloilo City, and the Holy Mary Women and Children’s Hospital in Pavia town which has a drive-thru specimen collection station.

The PRC laboratory in Passi City also conducts testing of collected samples from neighboring provinces including Capiz, Aklan, and Guimaras.

Registration for testing can be done online via the Philippine Red Cross website where clients can book a testing slot and pay for their tests online. The process aims to minimize physical contact between collection personnel and clients.

For Iloilo, online registration has not been available as of this writing, but Valderrama said that those who wish to get tested can go directly to the laboratory in Passi City or through the satellite collection centers.

The patients would then go to the collection site where they would show their registration number and unload their saliva into a Universal Transport Medium (UTM) vial, which comes with a barcode.

Prior to drooling, female clients would be told to remove their lipstick as it may contaminate the specimen.

Patients are advised to refrain from any oral activity for 30 minutes before drooling onto the vial.

The RT-PCR machine used for the saliva testing is tethered to a computer, which is then sends the results immediately to the patients themselves or through the satellite collection facilities.

The machine can test up to 1,000 saliva specimens per day, but the PRC only collects an average of between 100 to 500 specimens daily.

Valderrama said PRC’s saliva-based tests hit a 98 percent accuracy rate, and even reached 100 percent in May 2021.

He said they conduct parallel saliva test with clients who opted for swab-based extraction to compare and validate the accuracy of both methods. They began the parallel test at a ratio of 1 out of 10 and will eventually expand to 1:100 and even 1:1,000.

Saliva-based testing is currently being used in other countries including Japan, Thailand, Singapore, Australia, the United Kingdom, the United States, Israel, and Hong Kong, among others.

“Part of the requirements of the DOH and the RITM is for us to conduct a parallel test for every [patient under saliva testing]. Before it was for every 10 tests, we need to do 1 parallel test. The most recent result I have, which was done in May 2021, [showed] 100 percent or 10 out of 10. This means that for every 10 swabs, we also took 10 saliva samples and the results are all the same. Up to now, we are required to do parallel tests, so we ascertain that the accuracy will be up to standard,” Valderrama explained.

Valderrama also advocated for the saliva tests’ affordability, with their current rate at P2,000, compared to their swab-based RT-PCR tests which cost P3,800.

He said that the PRC’s aim in promoting saliva-based testing is to make “more affordable, non-invasive” COVID-19 testing more accessible to the people.

“Our aim is to make this a viable option to the people in the community. We do not see the hidden costs of quarantine people, where people and companies lose income due to the lack of work rendered as well as providing support. They would have options to get tested, and if they could be negative they could rejoin their company almost immediately. So, in a way, one can save in the long run,” he said.

He said that they are also working out deals to conduct specimen collection in other hospitals in the city and province of Iloilo.