The current pandemic of coronavirus has rapidly spread worldwide and it has resulted in approximately one million deaths so far (1). Early diagnosis and well-timed isolation of the infected individuals has now universally been accepted as an effective strategy of prevention and containment of local outbreaks of the coronavirus. With the sweep of the contagious variant of coronavirus, the omicron variant, even fully vaccinated individuals worry if they have contracted coronavirus when they have onset of flu and cold symptoms. This wondering can only be eased with the help of coronavirus testing.

To contain the spread of coronavirus infection, accurate and rapid tests are a crucial requirement. Polymerase Chain Reaction (PCR) test although very accurate the production of results takes a long time. In the present scenario where the main aim is to contain the spread of the virus, faster tests become indispensable and one such test is the rapid antigen swab test.

 

WHAT IS AN ANTIGEN RAPID SWAB TEST?

The protein present in the coronavirus is detected by an antigen determining whether the patient has coronavirus infection or not. The antigen testing is considered as the first line of defense test against the coronavirus especially in patients presenting coronavirus symptoms. This test involves a simple procedure and is quite quick in producing the result. However, the antigen test requires the viral load to be high in the nose and mouth to detect the virus (2).

 

HOW DOES AN ANTIGEN RAPID SWAB TEST PERFORM?

The antigen rapid swab test involves the use of a swab to collect the specimen from the nasopharynx or the throat of the patient. A sterile swab is used which is inserted into the nostril of the patient till the posterior nasopharynx surface or the sample is taken from the throat. After inserting the swab, it is rotated three to four times in the nasal cavity and then removed.

 

HOW DOES AN ANTIGEN RAPID SWAB TEST WORK?

Immune response in the body is produced in response to the substances known as “Antigen”. These substances trigger the generation of other substances in the body, the “Antibodies”. The antigen rapid swab test use antibodies made in a lab to detect the presence of antigens from the coronavirus.

Before performing an antigen test, a liquid is used to treat the sample. Soap and salt are present in this liquid that breakdown the cells and other units. This liquid is then applied to a test strip. Specific antibodies to coronavirus are already present on this test strip in the form of a thin line.

Similar to the antibodies present in the body, the ones present on the test strip will react with the antigen of the coronavirus present in the sample. If a colored line appears on the test strip, it indicates that the patient is infected with coronavirus (3).

 

WHY IS THERE A NEED FOR AN ANTIGEN RAPID SWAB TEST?   

After the genetic sequence of coronavirus become available in January 2020, molecular assays were quickly developed for diagnosis (4). A polymerase chain reaction is used by these assays for the amplification and detection of viral RNA. The sensitivity and specificity of these molecular assays are very high. But normally, these assays produce results in less than two hours but during the outbreaks, delay up to seven days have been observed in many countries (5). The risk of viral spread increases due to delays in the production of results. The longer wait by a patient means longer time he will take himself to isolate while carrying the virus. This makes antigen rapid swab tests essential for the identification of the virus in patients presenting symptoms of coronavirus.

 

BENEFITS OF ANTIGEN RAPID SWAB TEST

Several benefits are offered by the antigen rapid swab test. Some of the benefits are discussed below:

  1. Do not require complex laboratory equipment

Molecular assays are equipment-dependent. However, this is not the case with antigen rapid swab tests. Although, this test can be carried out in both a laboratory and at point-of-care, mostly this diagnostic test is available as a test kit in which the result can be read visually or a small portable device is used for processing and reading the result (6).

  1. Easy to Perform

The simple kits available for antigen rapid swab tests make them easier to perform and do not require a qualified person. These tests can easily be performed even in the comfort of the house (7).

  1. Cost-Effective

The fact, not much laboratory equipment is required for carrying out an antigen rapid test, makes it cheap and affordable (8). This makes it also cost-effective for repeated testing when required (9).

  1. Fast and rapid results

Molecular assays such as RT-PCR usually takes up to four hours to generate a result (10) while an antigen rapid swab test produces a result in fifteen to thirty minutes (11). In times of outbreaks, there is a special need to isolate infected people at early as possible. Getting tested with a molecular assay, the infected person will wait for the result before isolating himself resulting in the spread of the virus. While antigen rapid swab tests help in containing the virus by producing faster results so that the infected person can isolate himself without any delay.

  1. Easy availability

With the increase in demand for diagnostic tests for coronavirus due to outbreaks, a global shortage rises for the supply of cartridges and devices for molecular assay. Similarly, competition also exists for the procurement of reagents and other supplies which severely slows down the in-lab testing capacity of molecular assays (6). Antigen rapid swab test is not equipment dependent therefore do not need reagents, devise, cartridges, and supplies for its manufacturing.

 

THE BOTTOM LINE

The antigen rapid swab tests are cheap, quick, and easy to perform and do not require to be performed by a qualified and skilled person. It provides the ease of frequent testing in a cost-effective manner especially for those individuals who need to travel, return to work, and school. The rapid result offered by the antigen rapid swab test offers the opportunity of testing a large group of individuals in a community to curb the spread of coronavirus.

Sources

  1. Lippi G, Sanchis-Gomar F, Henry BM. Coronavirus disease 2019 (COVID-19): the portrait of a perfect storm. Ann Transl Med. 2020 Apr;8(7):497–497.
  2. Dinnes J, Deeks JJ, Adriano A, Berhane S, Davenport C, Dittrich S, et al. Rapid, point‐of‐care antigen and molecular‐based tests for diagnosis of SARS‐CoV‐2 infection. Cochrane Database Syst Rev [Internet]. 2020 [cited 2022 Jan 28];(8). Available from: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013705/full
  3. COVID-19 Antigen Test [Internet]. Testing.com. 2021 [cited 2022 Jan 29]. Available from: https://www.testing.com/tests/covid-19-antigen-test/
  4. FIND evaluations of SARS-CoV-2 assays [Internet]. FIND. [cited 2022 Jan 28]. Available from: https://www.finddx.org/covid-19/sarscov2-eval/
  5. McGarry BE, SteelFisher GK, Grabowski DC, Barnett ML. COVID-19 Test Result Turnaround Time for Residents and Staff in US Nursing Homes. JAMA Intern Med. 2021 Apr 1;181(4):556–9.
  6. Peeling RW, Olliaro PL, Boeras DI, Fongwen N. Scaling up COVID-19 rapid antigen tests: promises and challenges. Lancet Infect Dis. 2021 Sep 1;21(9):e290–5.
  7. Ciotti M, Maurici M, Pieri M, Andreoni M, Bernardini S. Performance of a rapid antigen test in the diagnosis of SARS-CoV-2 infection. J Med Virol. 2021;93(5):2988–91.
  8. Bekliz M, Adea K, Essaidi-Laziosi M, Sacks JA, Escadafal C, Kaiser L, et al. SARS-CoV-2 antigen-detecting rapid tests for the delta variant. Lancet Microbe [Internet]. 2021 Nov 24 [cited 2022 Jan 29];0(0). Available from: https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(21)00302-5/fulltext
  9. Larremore DB, Wilder B, Lester E, Shehata S, Burke JM, Hay JA, et al. Test sensitivity is secondary to frequency and turnaround time for COVID-19 screening. Sci Adv [Internet]. 2021 Jan [cited 2022 Jan 29]; Available from: https://www.science.org/doi/abs/10.1126/sciadv.abd5393
  10. Chaimayo C, Kaewnaphan B, Tanlieng N, Athipanyasilp N, Sirijatuphat R, Chayakulkeeree M, et al. Rapid SARS-CoV-2 antigen detection assay in comparison with real-time RT-PCR assay for laboratory diagnosis of COVID-19 in Thailand. Virol J. 2020 Dec;17(1):1–7.
  11. Guglielmi G. Fast coronavirus tests: what they can and can’t do. Nature. 2020 Sep 16;585(7826):496–8.

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