One of the reasons that why Singapore, South Korea and Taiwan are so successful in containing its COVID-19 outbreak is due to mass testing, quick identification and followed by isolation of infected individuals. Sadly, many countries including Malaysia are facing a shortage of testing equipment and facilities for COVID-19. On March 25, there were no COVID-19 cases being reported in Sabah, Malaysia due to unavailability of confirmation test. Therefore, there is an urgent need for a rapid, simple to use, sensitive, and accurate test to quickly identify infected patients of SARS-CoV-2 to prevent virus transmission and to assure timely treatment of patients.
What tests are available?
In Malaysia, the gold standard for diagnosing COVID-19 is the reverse real-time polymerase chain reaction (rRT-PCR) swab test. Read more about rRT-PCR here.
Another test that is available in Malaysia is the COVID-19 rapid test kit (RTK). Some called it IgG/IgM rapid test or serology test, well, they all meant the same thing. RTK is NOT a diagnostic tool for COVID-19, and it should only be used with a doctor’s advise.
How does COVID-19 RTK work?
COVID-19 RTK works by detecting two antibodies in a person’s body, i.e. IgM and IgG antibodies.
In general, the COVID-19 RTK would have simple anatomy as the following:
Image credit: Assay Genie
User is required to prick their finger (or draw their blood by a healthcare professional) and apply the blood onto the test strip.
Image credit: Assay Genie
If your blood contains IgM and/or IgG, they will meet and bind to the corresponding antigen conjugate in the conjugation pad. The combo would then travel across the test strip and meet the anti-human antibodies in M line and G line respectively, thus producing a coloured line (i.e. a positive result).
Fun fact: Do you know that the COVID-19 RTK actually shares the exact same principle as a pregnancy test strip?
The stories of IgM and IgG
When you are infected with COVID-19 (or any other viral infections), your body’s immune system would react by producing the antibodies named IgM and IgG. Antibodies are like the soldier your body sends to kill off the viruses. But both of them come in a different sequence, which IgM usually precedes IgG. People infected with SARS, for instance, produce IgM 3-6 days after infected, and IgG 8 days after infected.
In other words, if you are only detected with IgM, then there’s a chance that you are just infected not long ago. If IgG is detected instead, then it indicates that you have already been infected for a while.
It’s important to know that IgM and IgG are not specific to COVID-19 only. If you are infected with other viral infections such as SARS, MERS and Dengue, your blood may have IgM and IgG as well.
Why is COVID-19 RTK less reliable as compared to rRT-PCR?
It’s important that we mention that no test is perfect and 100% accurate, not even the gold standard rRT-PCR. However, in comparison, the COVID-19 RTK is less accurate than rRT-PCR, hence making it a less reliable test.
As the COVID-19 RTK detects antibodies that your body produces in response to the virus, it does not exactly tell you a lot about the COVID-19 virus in your body -- you can only know that the virus is in your body before, but you can’t be sure if they are still inside, or they have been cleared up by the body. And, if you think that feeling better (no fever, cough and other signs and symptoms) mean the virus has gone away, this is not true, as you can still carry the virus even though you do not feel sick.
But the real danger of using the COVID-19 RTK is this: there is a chance that an infected individual carries out the RTK on the first few days of infection and yield a negative result, as the body has not produced the antibodies yet. This can lead to letting go of a COVID-19 infected individual, and lead to a wider spread of the virus.
Image credit: NST
So who should use the COVID-19 RTK?
As of now, doctors would only prescribe RTK to those with mild or no symptoms. Any individuals with moderate or higher risk SHOULD NOT use RTK and should get the rRT-PCR swab test instead.
I think I am low risk. Can I just purchase any COVID-19 RTK online without a doctor’s consultation?
No, you should not.
Firstly, it may not be wise for you to decide what risk you have. We strongly encourage you to talk to our COVID-19 Task Force on the Doc2Us® app and let the online doctors advise about your COVID-19 risk and which test you should get.
Secondly, should you need to carry out the test, our doctor would provide counselling after you have done the test as per the instructions.
Remember, carrying out a rapid test kit WITHOUT a doctor’s consultation is an incomplete process and can even be dangerous.
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