Different rapid antigen tests and how they work

For around 20-30 years, PCR has been extensively utilized in research and medicine to discover genetic information. RT-PCR is a modified form of the method that is utilized when RNA is identified, and it is currently being used to identify SARS-CoV-2, the virus that causes COVID-19. This sort of rapid antigen tests has commonly been employed as a first-line diagnostic for COVID-19 because it detects the viral RNA directly.

RT-PCR assays are relatively rapid, sensitive, and reliable, with findings available in 3-4 hours, however, this time is often extended if samples must first be forwarded to specialized external labs (6-8 hours on average).

Numerous diagnostic and research businesses manufacture RT-PCR products, tests, and equipment, ensuring widespread availability of the technique. Certain RT-PCR assays are produced as an ‘all-in-one’ kit, which minimizes laboratory handling and contamination risk.

How it operates

After collecting a sample, chemicals are employed to deplete it of proteins, lipids, and other components, leaving just RNA. This will be a combination of the individual’s genetic material and any viral RNA that may be present.

The enzymes in the rapid antigen tests kit convert the RNA to DNA, which is amplified to enable virus identification using a PCR machine that cycles the rapid antigen tests temperature in such a way that about 35 billion copies of viral DNA are produced for each viral RNA strand that was initially present.

Typically, fluorescent markers are employed to attach to amplified DNA and generate light that can be read by the machine to provide the rapid antigen tests result. A positive rapid antigen tests is one in which the intensity of the light emitted inside the sample exceeds a predetermined threshold. The number of PCR temperature cycles necessary to attain the fluorescence threshold is recorded, providing an estimate of the viral load in the patient sample.

What are rapid antigen tests designed to detect?

RT-PCR is used to determine whether or not viral RNA is present in patient samples. This is accomplished by encoding and amplifying segments of the virus’s genetic material, often the Spike protein, the N protein, or the Envelope (see picture).

To quantify viral RNA, it is transformed to DNA, duplicated several times using multiple temperature cycles in a PCR machine, and then detected using fluorescent markers. If the quantity of fluorescence increases over a specific threshold, this indicates the presence of the virus. The number of temperature cycles required for the machine to attain this threshold is recorded in order to determine the amount of virus contained in the patient sample. The fewer cycles, the greater the amount of virus present. Typically, these samples are obtained by swabbing the nose or throat with either long or short swabs, although they may also be obtained in other methods. Collecting samples from areas where the virus is shed or proliferating increases the rapid antigen tests‘ accuracy. Click here to read how to use a rapid antigen test kit.

What does the outcome imply?

When conducted on a sample from an infected area of the body during an active illness, an RT-PCR rapid antigen tests is very sensitive and moderately reliable.

A positive PCR result indicates that the individual from whom the sample was collected is presently infected with the virus.

Negative PCR result: – A negative PCR result may indicate that the individual is not presently infected with this virus, the virus is not present at the place from where the sample was collected, the sample was of low quality, or the infection is too early or late to detect the replicating virus. This is why negative test findings need the collection of fresh patient samples a few days later to eliminate the possibility of missing an infected individual.

The RT-PCR rapid antigen tests cannot determine if a person had the virus and subsequently cleared it after the end of the COVID-19 sickness, or whether a person had the disease since it detects an only active virus.

Advantages and disadvantages

  • RT-PCR is widely acknowledged by scientists and medical personnel as a reliable and well-documented technology.
  • Because RT-PCR is so widely used in research and medicine, the technology for rapid antigen tests for COVID-19 is already in place.
  • RT-PCR may identify active illness infections, enabling medical personnel to decide who is infected and who is not.


  • Because RT-PCR is based on collecting and identifying viruses, it may overlook individuals who have cleared the virus and recovered from sickness. learn more ways of recovering form sickness at
  • Because viral distribution in the respiratory tract differs across individuals, even if a person is infected, the virus may be detected only in sputum or a nasopharyngeal swab, but not always in both sites concurrently.
  • Real-time polymerase chain reaction (RT-PCR) for COVID-19 can only determine whether a person is presently infected with this specific coronavirus. It is unable to offer information on further illnesses or symptoms.

Antigen examinations

Rapid and precise rapid antigen tests is critical for the containment of a highly infectious virus such as SARS-CoV-2. While PCR tests are reliable, they might take a long time to complete. While rapid antigen tests, the second primary form of coronavirus test, are much quicker, they are also significantly less accurate.

Antigens are substances that elicit an immunological response in the body — they initiate the production of antibodies. These assays look for antigens from the SARS-CoV-2 virus using laboratory-made antibodies.

To conduct an antigen test, a sample is first treated with a solution comprising salt and soap, which dissolves cells and other particles. Then you add this liquid to a test strip that has been coated in a narrow line with antibodies specific for SARS-CoV-2.

Antibodies on the test strip, like those in your body, will bind to any antigen in the sample. If the antibodies recognize coronavirus antigens, a colored line indicates the presence of SARS-CoV-2 on the rapid antigen tests strip.

Antigen testing provides a variety of advantages. To begin, they are so simple to do and interpret that …

A critical look at rapid antigens tests

The coronavirus epidemic continues to have a significant impact on our everyday lives, infecting hundreds of thousands of individuals each week. COVID-19 rapid antigen tests are a very effective method of protecting yourself and your family. However, which exam is appropriate for you? Dr. Christopher Carpenter, a Beaumont infectious disease specialist and chair of internal medicine, has the answers.

What are the many COVID-19 test types?

There are two primary kinds of COVID-19 rapid antigen tests available at the moment.

  • Viral testing may be used to determine whether a person is currently infected with COVID-19. Nucleic acid amplification rapid antigen tests (NAATs) and antigen testing are two frequent forms of viral diagnostics. You may have heard NAATs referred to as polymerase chain reaction (PCR) testing. Vaccination will not result in a positive result on these rapid antigen tests.
  • Antibody rapid antigen tests, often called serology tests, may determine whether you have ever been infected with the coronavirus, but they cannot identify an active infection. Depending on the antibody target (i.e., those directed against the spike protein), this test may potentially detect a response to past immunization in an individual who has never been sick.

While certain viral tests may be performed on-site or even at home, others must be transported to a laboratory for processing.

“While on-site testing is convenient and produces findings quickly, it has significant limits,” Dr. Carpenter said. “In many circumstances, operators are restricted in their ability to complete a particular number of rapid antigen tests within a certain amount of time. Sensitivity and precision might sometimes be a problem.”

While laboratory tests are more precise, they may take longer to complete.

Which Examination Should You Take?

“Which test is best for you is situation-dependent,” Dr. Carpenter said. “Some rapid antigen tests are only authorized for persons who are already experiencing symptoms, and they should not be used for screening if you are feeling well. The best test is one that provides the most accurate result in the shortest amount of time.”

When time is critical, an antigen or fast test may be the best option. Numerous rapid antigen tests are now accessible as home test kits, which eliminates the need to visit a health care institution. If you have the patience to await the findings of a laboratory-based test, you will often obtain the most accurate results. learn more about rapid antigen tests by clicking here.

While no test is perfect, the ones now available are very accurate when done properly. If you choose an at-home test, it is critical to carefully follow the directions for the best results. Individuals who continue to suffer symptoms after a negative COVID-19 test may seek repeat testing.

When should you get tested for COVID-19?

COVID-19 rapid antigen tests are beneficial for confirming or ruling out an infection, particularly as we approach flu season. Not only may the outcome impact treatment choices, but it can also assist safeguard individuals in your immediate vicinity. learn more about clinical supplies at

The CDC advises that everyone who exhibits symptoms consistent with COVID-19 be tested, even those who are completely vaccinated or have been infected before. Additionally, those who have not been vaccinated but have traveled, attended big meetings, or been in poorly ventilated interior settings should be examined.

Individuals who have been completely vaccinated and have been exposed to someone who has COVID-19 should seek rapid antigen tests to confirm they have not caught the virus. While the individual may be symptom-free, they may still transmit the illness to others. If positive, rapid antigen tests assist in preventing this with adequate isolation.

  • If you feel you have been exposed to COVID-19 and are completely vaccinated, you should test 5-7 days following your original exposure. 
  • If you believe you have been exposed to COVID-19 but are not fully vaccinated, you should test immediately. If your test result is negative, be certain to retest (5-7 days after the initial exposure or immediately after symptoms develop).

Anyone wanting to go overseas or returning to the United States after an international trip may be needed to have a recent negative COVID-19 test. Because specific restrictions vary per location, it is important to verify and make the necessary preparations before visiting.

How to safeguard oneself while awaiting test results

“If you are asymptomatic and undergoing regular rapid antigen tests, such as before to travel, there are no restrictions other than the advised precautions,” Dr. Carpenter says.

Individuals who have not been vaccinated and have been exposed to COVID-19 should consider self-quarantine. Individuals who have been vaccinated may not be required to quarantine, but they should check themselves for signs and continue to take measures. The CDC advises isolation for anybody exhibiting COVID-19 symptoms while awaiting test results.

Despite extensive rapid antigen tests, Dr. Carpenter underlines that immunization remains the most effective method of preventing COVID-19.

Investigating genetic evidence

For any kind of test, the initial step is to get a sample from the patient. This might be a swab of the nose or a little amount of saliva.

For PCR rapid antigen tests, the following step is an amplification of the genetic material, which allows for detection of even a minute quantity of coronavirus genes in the patient’s sample. This is accomplished via the use of a process known as a polymerase chain reaction. A health care professional collects the sample and uses an enzyme to convert it to double-stranded DNA. 

The DNA is then heated in the presence of a solution containing an enzyme called a polymerase, causing it to split into two single-stranded DNA fragments. The temperature is dropped, and polymerase attaches to and replicates the single-stranded DNA with the assistance of a short bit of guide DNA called a primer. The primers are designed to amplify just coronavirus DNA. You have now replicated coronavirus DNA twice from the initial RNA fragment.

Laboratory machinery performs these heating and cooling cycles 30–40 times, doubling the DNA to a billion copies. …