MANILA - The Philippine Red Cross stands by the integrity of its RT-PCR tests which have been assailed by some lawmakers and President Rodrigo Duterte for allegedly yielding false positives.
In a statement, the PRC confirmed it had to retest some samples in Subic, which yielded positive results possibly due to cross contamination.
"The testing samples alluded to in the hearing at the lower House pertain to samples taken at the Unihealth-Baypointe Hospital and Medical Center in Subic Bay Freeport Zone by their personnel and tested at the PRC Molecular Laboratory also in Subic Bay Freeport Zone. Of the 48 samples, 45 turned out positive, triggering a complete re-run and a manual process to eliminate the possibility of erroneous results, which may be caused by cross-contamination," it said.
PRC said it re-tested those in the affected samples on its own and the results are the same.
"This is an example of a situation where the PRC, on its own initiative and at its own expense, requires an automatic re-run by its molecular labs in order to ensure the accuracy of results. On the second run, the results came out exactly the same. The Subic laboratory followed standard operating procedures and quality assurance guidelines as it has done for all 122,000 samples processed by the Subic lab from July 1, 2020 to September 3, 2021," it explained.
PRC attributed to differences in timing of the tests the difference in results.
"The negative result of the tests in question came from specimens collected after three days, which may be one such factor for the negative result. Clients may have truly been negative already by the time their second sample was taken. The sampling method (in this case, sampling was performed by Baypointe Hospital personnel), test kits, extraction method, and the thermocycler (PCR machine) used by the testing laboratory are also factors that may influence the results," it added.
PRC also acknowledged the possibility of false positives.
"While we strongly stand by the integrity of the positive results issued by our Subic laboratory on the samples, we acknowledge the possibility of false positive results since no test is 100% accurate. In such cases, the Department of Health encourages us to err on the side of caution and treat all positive results as true positive. This is designed to protect everyone, including the clients and their families and co-workers. This is especially true for healthcare workers who are constantly at risk of exposure to the virus," it said.
PRC explained it operates 13 molecular laboratories throughout the country, and the test methodology and procedures are standardized in all its laboratories.
It also said it is subjected to Research Institute for Tropical Medicine's PT every time a laboratory opens and that the issuance of the License to Operate by the Department of Health (DOH) is dependent on passing the proficiency test with a 100% score.
PRC also said this test and the strict implementation of quality standards in all PC laboratories based on protocols set upon by manufacturers, in line with the standards set forth by the DOH and the RITM, assure the public of the accuracy of test results released by PRC.