RT-PCR vs Rapid Antigen Tests
Now that we have a better understanding of antibody tests, let’s talk about the viral tests, which, in the Philippines, are divided into RT-PCR and rapid antigen testing.
RT-PCR, which stands for Reverse Transcription-Polymerase Chain Reaction, uses laboratory equipment to look for the genetic material of SARS-CoV-2. You need to wait for at least 24 hours before you get your result.
On the other hand, rapid antigen tests look for certain proteins attached to the virus. Unlike RT-PCR testing, antigen tests use just a small kit and their results come out after just a few minutes. Hence, we call it a “rapid antigen test.”
Note that RT-PCR testing is more accurate because it is more specific as it looks for the viral genetic material. For a rapid test to be accurate, it has to satisfy certain criteria, such as the time of testing. Testing too early or too late can give you a false-negative result.
Saliva COVID Test vs Nasopharyngeal Swab Test
Usually, when people mention “swab test,” we assume that they’re talking about RT-PCR swab testing. But, that’s not the case. You see, both saliva and swab samples (from throat and nose — nasopharyngeal or NP) can be run through RT-PCR machines or rapid antigen kits.
Hence, you have a NP swab RT-PCR test and saliva RT-PCR test (just like the one offered by the Philippine Red Cross). You also have a rapid antigen swab test and a rapid antigen saliva test.
In terms of accuracy, the RT-PCR NP swab and saliva COVID test are more accurate than NP swab or saliva antigen tests.
Nasopharyngeal RT-PCR testing still remains the gold standard for detecting SARS-CoV-2 Omicron variant. However, salivary RT-PCR can be used as an alternative screening method in case of any contraindication in performing NP sampling.
When Should You Have What Test?
At this point, you must be wondering: When do I need a saliva COVID test? When is it necessary for me to have RT-PCR testing?
The answer depends on why you are taking the test.
If you need to confirm COVID-19 infection for diagnosis, you need to undergo an RT-PCR NP swab test as it is still the gold standard for COVID-19 testing. Case in point: you may not get the PhilHealth Benefit Package for COVID-19 unless an RT-PCR NP swab test confirms your infection.
Now, if you suspect an infection and do not need the more expensive RT-PCR testing, a rapid antigen test may suffice. However, you may not get accurate results if you take it at the wrong time.
For travel, you may want to check the policy in your destination. Some require RT-PCR testing, while others may be more lenient and accept antigen results.
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