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Opor P. Suthini

26 Jul 2021 - 6 min read

Rapid Antigen Test vs Rapid Antibody Test: What’s the difference? How to do a home test kit in 30 minutes?

Rapid Antigen Test vs Rapid Antibody Test

Following the increased severity of the Covid-19 pandemic situation in Thailand, news spread quickly of the decision by the Ministry of Public Health approving of hospitals using Rapid Antigen Tests to do screenings for their patients and for those at risk in-line waiting treatment. Soon after, the Ministry also approved the Antigen Test Kits (ATK), now allowing Thai citizens to buy and use these kits by themselves at home. This is likely due to the overwhelming number of cases in all hospitals causing further delays in finding those who are positive of Covid-19, and the growing need to find and isolate those who are infected faster.

Currently, there are 3 types of Covid-19 tests in Thailand: Real-Time PCR Test, Antigen Test, and the Antibody Test. In some countries there might also be another type available, which is the ECLIA (Electrochemiluminescent Immunoassay) Test. Each test type has its own merits and benefits, and known levels of accuracy. Learn more about the types that suit you at here. As mentioned earlier, the Ministry may have green-lit the Antigen Test Kit, but you might still have questions of what they can tell you, and what the Antibody Test Kit, currently still unapproved, will tell you. Let’s compare both test kits and learn how to use them correctly.

Rapid Antigen Test

Rapid Antigen Test tests for the presence of the virus through nose swab to find the protein strand of Coronavirus. Antigen Test is a “quick screening” before thorough lab test or RT-PCR Test, and can tell you whether there are active viruses in your body. In order to use the Antigen Test Kit correctly, you must learn how to use the kit and read instructions on the box carefully. You must also know how to dispose of the kit safely after using it to avoid spreading the virus to others. Find out how to collect nasal sample with the Antigen Test Kit (ATK) here:

rapid-antigen test en

Covid-19 Rapid Antigen Test Procedure

How to use the Antigen Test Kit:

1.
Wash your hands thoroughly.
2.
Prepare the vial of the lysis buffer included in the kit.
3.
Take the swab stick out and gently push it into your nose according to the depth suggested on the swab stick. Turn 3-4 times, then let it soak there for about 3 seconds.
4.
Put the swab stick with the sample into the vial of lysis buffer. Turn the stick around in the vial 5 times.
5.
Suck the liquid from the vial, drop 3-4 drops onto the hole of the test kit.
6.
Wait 30 minutes.
7.
Check the results. 1 line means no virus detected (NEGATIVE), 2 lines mean virus detected (POSITIVE)
8.
If the result is positive, you must confirm the infection with a RT-PCR Test

What to know: You should do the test kit immediately once you show symptoms of Covid-19. In the case that your body has started showing Covid-19 symptoms more than 5 days, the kit may not detect the amount of the virus in your system.

From July 6th 2021 onwards, Thai citizens can find Rapid Antigen Test Kits from pharmacies and other online vendors. Don’t forget to look for the test kits with FDA approval by the Ministry.

Check which Antigen Test Kits are FDA approved here

Rapid Antibody Test

Rapid Antibody Test is a test to detect antibodies against Covid-19 through the process of taking blood samples from the tip of the finger. Many countries allow sales of Antibody Test in stores, but Thailand has not approved of the Antibody Test Kit yet due to the rollout timeline of vaccination and the period of immunity building in those vaccinated not aligning with this type of test yet.

Rapid Antibody Test can detect 2 types of antibodies in the body:

Immunoglobulin M (IgM) - Found in blood and lymph, IgM is the first antibody the body produces to fight the virus during the initial infection. IgM is considered the first line of defense against real infection, before the body creates other antibodies in the body.
Immunoglobulin G (IgG) - Most commonly found antibody in the body, found in blood and other bodily fluids. This is the antibody which takes some time to build in the human body after infection or vaccination.

Check out how to collect blood sample for research with the Antibody Test Kit here:

covid antibody test EN

Covid-19 Rapid Antibody Test Procedure

How to use the Antibody Test Kit:

1.
Wash your hands thoroughly.
2.
Wipe alcohol on the finger you’re taking the blood sample from.
3.
Pinch the tip of the finger with the tool, wait for blood to pool up.
4.
Use the tool to suck blood drops from the finger and drop 2-3 drops onto the portable test kit. Then, drop 2-3 drops of the test solution in to mix with the blood.
5.
Wait 15-30 minutes.
6.
Check the results. 1 line means antibody is undetected, 2 lines or more means antibody (either IgM or IgG, or both is detected)

What to know: Best period to do the Antibody Test is around 7 days or more after contact with those at risk or those infected, since it is the time frame your body builds antibodies to fight the virus. Your body may not have built antibodies against the virus earlier than 7 days of infection or contraction.

As mentioned earlier, Thailand has not approved of the Antibody Test Kit for personal use yet. If you need to test for Covid-19 antibodies in your body, you must go directly to the hospital, or a lab which can provide a full test.

Other than the well-known Antibody Test you have heard talked about often during these last months, in some countries, another type of test is available. The ECLIA of Electrochemiluminescent Immunoassay detects the presence of IgG and IgM antibodies in individuals. ECLIA Test is done in a laboratory with equipment and a program specific to finding antibodies, takes about 10-15 minutes, and provides results within 1-2 days.

Compared to the Rapid Antibody Test, the ECLIA Test is less sensitive in detecting the antibodies. It can detect fewer antibodies while costing generally the same as the Rapid Antibody Test. The ECLIA Test can not be used for travel like the RT-PCR Test or Rapid Antibody Test. Keep in mind that if you want to test for the Covid-19 virus, the RT-PCR still provides you with the most accurate results compared to other tests.

ECLIA Test EN version

Covid-19 ECLIA Test Procedure

Real-Time PCR in EN

Covid-19 RT-PCR Test Procedure

What to do if you’re traveling out of dark-red provinces?

Thailand is in current lockdown of 29 provinces including Bangkok, Chachoengsao, Chonburi, Nakhon Pathom, Nonthaburi, Narathiwas, Pathumthani, Pattani, Ayutthaya, Yala, Songkhla, Samut Prakan, Samutsakorn, Kanchanaburi, Tak, Nakhon Nayok, Nakhonratchasima, Prachuap Khiri Khan, Prachinburi, Ranong, Phetchabun, Phetchaburi, Ratchaburi, Sing Buri, Lopburi, Samut Songkhram, Saraburi, Sing Buri, Suphan Buri and Ang Thong. These are what you need to prepare or acquire if it is necessary for you to cross between or from dark-red and red province borders.

Register on https://covid-19.in.th/
Get proof or document permitting travel from your local authorities such as sub-district headman or district officer
Keep the QR Code from the site with you. This QR Code will be necessary during the border crossing process of any of the 13 provinces

Sources:

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