For Dr. Dean Hernando A. Zenarosa, consulting physician of the Philippine Information Agency, timing is everything when administering reverse transcriptase polymerase chain reaction (RT-PCR) or swab test in order to rule out COVID-19 infection.
Tests for severe COVID-19 on reverse transcriptase polymerase chain reaction (RT-PCR) are being used to rule out infection among high-risk persons, such as exposed inpatients and health care workers.
"If you think you were exposed or know somebody who was, don’t immediately rush to the nearest swabbing center. Timing is everything. Coming in too early or too late might give a more confusing result," Zenarosa said.
The healthcare worker based his medical opinion on the Annals of Internal Medicine, where one study said it is critical to understand how the predictive value of the test varies with time from exposure and symptom onset to avoid being falsely reassured by negative test results.
"If you think you have been exposed to a person with COVID-19 and you need a swab test to be certain, the sensitivity of your swab test is affected by timing of collection and amount of virus, if present, in your body," he added.
Zenarosa deatailed the guide, as follows:
Day 1 of exposure: 0%
Day 4 of exposure: 33%
Day 5 of exposure, 1st day of symptoms: 62%
Day 8 of exposure, 3rd day of symptoms: 80%
Day 21 of exposure, likely no more symptoms: 34%
*Source: www.acpjournals.org
The physician recommends the time to do a swab test is between the first to third day of symptom onset.
"Testing is not advisable for asymptomatic individuals without knowing the time of exposure due to high false negative rates," Zenarosa said.
"For symptomatic people, have it done first to third day of symptom onset is best," he added. (PIA NCR)
Source: Philippines Information Agency (pia.gov.ph)
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