COVID-19 test results from different test dates may vary — DOH

MANILA, Philippines — COVID-19 test results on samples taken from a common patient in two different time points may vary, the Department of Health (DOH) said Tuesday after President Rodrigo Duterte claimed there were “false positive” results in tests made by the Philippine Red Cross (PRC).

According to DOH Undersecretary and spokesperson Maria Rosario Vergeire, laboratory test results can be influenced by multiple factors.

“The outcome of a laboratory test result is influenced by multiple factors, affecting all the phases of testing from pre-analytic, analytic to post-analytic (from specimen collection, specimen transport, specimen evaluation, nucleic acid extraction, testing, results analysis, verification and releasing),” Vergeire said in a statement.

“Additionally, it is possible for test results from the same case collected at two different time points to vary, potentially due to the timing of specimen collection (depending on the clinical course of infection) and other possible sources of variation in the pre-analytical, analytical and post-analytical phases,” the health official added.

Vergeire said all tests have to be interpreted using the “epidemiological and clinical situation” of the patient.

In his taped briefing aired on Monday, Duterte said the DOH should look into the supposed false positive test results from the PRC. According to the President, 44 out of 49 hospital personnel who were tested in PRC laboratories initially tested positive but turned out to be negative for the virus in another laboratory.

He also claimed that 187 out of 213 members of the Presidential Security Group tested positive in a PRC laboratory in Manila but later tested negative in a confirmatory test.

Meanwhile, Vergeire stressed that RT-PCR testing remains to be the gold standard in confirming the presence of SARS-CoV-2 on a person, and that the test kits being used in the country have been evaluated by the Research Institute for Tropical Medicine.

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