Study recommends pooled testing
A Project Ark-funded study on COVID-19 is recommending pooled testing of five people at a time, using one swab test kit, which would cost P650 to P700 per person. The Philippine Society of Pathologists Inc. and Philippine Children’s Medical Center conducted the research to find a more affordable but accurate way of screening people asymptomatic of the virus.
A study funded by Project Ark is recommending pooled testing of five people at a time, as it has found that testing a bigger group might dilute the results and miss out on those positive for the new coronavirus.
Testing five asymptomatic people using one RT-PCR testing kit, or reverse transcription-polymerase chain reaction, would cost P650 to P700 per person, a cost saving of up to 70 percent, according to a Zoom presentation of the study.
The Philippine Society of Pathologists Inc. and the Philippine Children’s Medical Center conducted the research, which sought to find a more affordable yet still accurate way of screening people for the virus that causes COVID-19.
Pooled testing is an RT-PCR test done in groups. A positive pooled testing result would require more individual testing, without the need for getting new swabs, until authorities locate the coronavirus positive person.
The study was done in batches of five, 10 and 20. It did both a simulation of pooled testing using samples and an actual pooled testing of over 400 supermarket workers, wherein 3 percent were found to be COVID-19 positive.
Bigger pool, weaker sensitivity
The simulation showed that the sensitivity of the tests might get weaker as the pool got bigger.
“So we are actually recommending a pool size of five for faster turnaround time with comparable saving and the least drop in sensitivity. That is our preliminary finding as far as this research is concerned,” said pathologist Raymundo Lo, principal investigator of the study.
In the simulation, a pool of five showed a sensitivity of 83 percent. The sensitivity dropped to 72 percent in a pool of 10 and to 67 percent in a group of 20.
“[W]e have detected a little drop in sensitivity. But that is to be expected as
well as seen in the other pooled testing studies abroad,” Lo said. “This does not negate the benefits of pooled testing.”
He said testing a larger population would still yield more COVID-19 carriers than not testing at all, even if pooled testing were to miss some people who had low viral loads.
Lo recommended that pooled testing be done only to select groups, including low prevalence communities; hot zone communities; health-care workers; factory workers, market vendors, call center and transportation workers; airports and seaports for inbound foreign travelers and returning residents.
Pooled testing was also recommended for the deployment of overseas Filipino workers (OFWS), returning OFWS, frontline government workers (police, military, quarantine, immigration officers to name a few), and locally stranded individuals.
The study was conducted together with the Research Institute for Tropical Medicine and the University of Perpetual Help Dalta Medical Center as research study sites, according to a Project Ark statement after the Zoom presentation.
Private sector partners, through Joey Concepcion’s Go Negosyo, supported and funded the research.
Pilot testing in Metro
“The private sector will fund a pooled PCR testing pilot for 16 cities and one municipality in [Metro Manila] this month. That represents about 160,000 pooled PCR tests that will be done for this part of the research,” Concepcion, presidential adviser for entrepreneurship, said in a statement.
“This will be a game changer for our country. We will also bring more private sector companies to support more cities in
NCR. It could speed up testing, increase the capacity and make it cheaper. Testing will create greater visibility,” he said.
Makati City will be the first to conduct pooled testing, although it was supposed to start on Aug. 15. They hope to do the testing this week.
The controversy surrounding rapid antibody testing—a cheap and quick method that Concepcion advocated—would likely haunt this new method that he now is pushing for.
False negatives
On Monday, Trade Secretary Ramon Lopez said rapid antibody tests should not be used on workers amid fears that false negatives under the quick and cheap tests may have contributed to the surge in infection.
Although he did not say if he was referring to Concepcion, Lopez reminded the public that they should not listen to advocates of rapid antibody testing. Instead, he emphasized that only RT-PCR testing should be used.
“What’s needed is RT-PCR for those who are symptomatic,” he said in an event on Facebook live on Monday.
While Lopez warned against the controversial rapid antibody test kits, he said that only symptomatic and exposed workers were required under the new guidelines to be tested. In these cases, the employers should shoulder the expenses.
The Department of Trade and Industry and the Department of Labor and Employment issued new work protocols over the weekend. For some reason, however, the two agencies required testing only workers that show COVID-19 symptoms, although asymptomatic workers could be silent carriers of the virus.
Concepcion, who led Project Ark, said in an earlier press briefing on Zoom that the main cause of the surge was testing at the start only symptomatic people.