What Are The Types Of COVID-19 Rapid Antigen Tests?

COVID-19 Rapid Antigen Tests (RATs), which detect the presence of SARS-CoV-2-specific proteins (antigens), are increasingly being used by the public to quickly check for a COVID-19 infection. With the development of rapid antigen tests, quick, convenient, and frequent testing has become available to wide populations. As our technology catches up with novel data and public demands, different types of rapid antigen tests have been developed for COVID-19.

Today, we are presented with more options than ever, and while this growing variety offers many advantages, it may be difficult to choose the best option for your specific conditions and needs.

The main principles of rapid antigen tests remain similar. However, they are classified based on their differences regarding their target region, usage area, and sampling procedure. As these differences may have significant implications for your comfort, convenience, as well as the test performance, it may be beneficial to get informed before taking a test. Below, you can find up-to-date information on different types of rapid antigen tests which may help you evaluate each option according to your needs and conditions.

Types of COVID-19 Rapid Antigen Tests Based on Target Region

In the market, you can find different COVID-19 rapid antigen tests by their target region. Usually, the target region selection was alternated between two proteins: spike and nucleocapsid. Spike proteins are the surface proteins of the SARS-CoV-2, and the virus binds to the host cells by these proteins. On the other hand, nucleocapsid proteins are located surrounding of the RNA molecule to protect the genetic material.

Usage of spike protein regions as target is more common however, the mutations are mostly carried on these proteins. This situation may affect the accuracy of the rapid antigen tests using spike protein as target region.

Types of COVID-19 Rapid Antigen Tests Based on Sampling and Procedure

Swab Sampling Types for COVID-19 Rapid Antigen Tests

By definition, a swab is a small piece of soft, absorbent material on the tip of a long, flexible stick. A rapid antigen test using swab sampling typically requires the collection of nasal, nasopharyngeal, or oropharyngeal specimen by a sterile swab.

For rapid antigen tests that use nasal samples, the swab needs to be inserted about 2.5 cm into a nostril and rotated slowly for a few times before its removal as instructed. The same procedure must be performed for the other nostril.

For the nasopharyngeal swab sampling, the swab needs to be inserted through the nasal cavity until it reaches the upper part of the throat behind the nose, or the nasopharynx. Then, the swab is slowly rotated a few times as instructed, and removed.

For oropharyngeal swab samples, the swab needs to be inserted into the mouth until it reaches the back of the throat. Then, the swab is rotated slowly for a few times as instructed and removed.

Saliva Sampling Types

Alternatively, some rapid antigen tests for COVID-19 use saliva specimen without swab usage to detect the presence of SARS-CoV-2. Sample collection may involve saliva swabs, saliva tubes or saliva lollipops.

For saliva swab sampling, place the swab under the tongue for 10 seconds, rotate 5 times and soak it completely.

For saliva sampling without swab requirement, an apparatus or a disposable dropper are usually used.

Procedure of sampling with an apparatus can be summarized as following: Open the collection tube which is filled with extraction buffer. Carefully place the collecting apparatus to the mouth of the tube. Put your saliva sample into the collection tube with the help of apparatus.

On the other hand, sampling with a disposable dropper is as following: Put your saliva to the aluminum foil package. With help of a disposable dropper, take 1 ml (3 drop) of saliva.

In addition to other test procedure for saliva sampling, there is one other test type: Saliva-lollipop testing. In this type of testing, you do not need any other instruments but test cassette.

Although saliva tests may be more comfortable to perform, experts warn that as the mouth is a relatively more open environment than the nose, the specimen might be more vulnerable to contamination. Accordingly, it is recommended that the person taking the test should not eat, chew, drink, smoke, or vape for at least 30 minutes before performing the test. Saliva tests also may not be the best option for people with low saliva production, such as very young children or people who have suffered a stroke.

Types of COVID-19 Rapid Antigen Tests Based on Usage Area

Some rapid antigen tests are exclusively designed for professional use. Rapid antigen point-of-care tests can be carried out outside of the laboratory by healthcare professionals and trained persons under their supervision. These tests enable the rapid detection of a SARS-CoV-2 infection in near-patient settings and at the site of care and treatment. Professional administration provides maximum accuracy and safety by ensuring sufficient sample collection, correct interpretation of the results. Moreover, following the test, the patient can immediately access clinical guidance and treatment if necessary.

As opposed to professional-use tests, rapid antigen self-tests are designed to be administered without the involvement of a healthcare professional or trained person. Self-tests can be performed wherever, whenever, and as often as needed without supervision. These tests require the person taking the test to collect the specimen, perform the test, and interpret the results in accordance with the instructions provided within the kit. Unlike self-sampling PCR tests where the collected specimen must be sent to a laboratory, self-test kits do not require laboratory equipment for sample procession. Therefore, just as professional-use tests, self-tests provide results at the point of testing without delay.

Rapid antigen self-tests for COVID-19 are available online, as well as in pharmacies and retail stores without prescription in some countries including U.S., Germany, France, Italy, U.K., and Vietnam. Although self-tests typically involve user-friendly equipment, simple steps, and easy-to-interpret results, it is decisive that the person taking the test fully understands and follows the instructions provided within the kit to minimize the risk of inaccurate or invalid results.

Moreover, Self-tests often use nasal or saliva specimen since the collection of these samples cause minimal discomfort and require the least expertise. To minimize discomfort and sampling errors, procedures that involve deeper insertion such as nasopharyngeal and oropharyngeal swabs are usually intended for professional use.

Conclusion

With rapid antigen tests for COVID-19 is now faster, more accessible, and more convenient than ever before. Today, there are a variety of rapid antigen tests available for the public. Depending on its target antigen, usage area, and sample type, different tests may suit different needs. Getting familiar with various types of rapid antigen tests could help us determine the best option available according to our needs and conditions.