Rapid antigen tests are intended to determine an individual’s infectious status in a matter of minutes. Are they going to be game-changers?
The United States leads the world in COVID-19 deaths but lags behind a number of countries, large and small, in terms of testing capacity. That could change in the near future.
The US Food and Drug Administration (FDA) granted emergency use approval to a new credit-card-sized coronavirus testing device that costs $5, provides results in 15 minutes, and does not require a laboratory or processing machine. The United States is spending $760 million on 150 million of these amazing rapid antigen tests from Abbott Laboratories, based in Abbott Park, Illinois. Abbott Laboratories plans to increase production to 50 million per month in October.
The rapid antigen tests look for specific proteins on the surface of the virus called antigens and can identify individuals who are at the peak of infection, when virus levels in the body are most likely to be high. According to proponents, this could be a game changer. Antigen tests may help avert a pandemic, as they can be administered in large numbers and can identify those most at risk of spreading the disease. These rapid antigen tests are also a critical component of other countries’ testing strategies, such as India and Italy.
Antigen assays are significantly faster and less expensive than gold-standard rapid antigen tests that employ a technique called the polymerase chain reaction to detect viral RNA (PCR). However, antigen tests are not as sensitive as polymerase chain reaction (PCR) rapid antigen tests, which can detect trace amounts of the SARS-CoV-2 virus that causes COVID-19. Click here to check some of the common questions that people usually ask about the rapid test.
This discrepancy concerns some specialists, who fear that antigen tests will miss infectious individuals, resulting in outbreaks in countries where coronavirus transmission is largely controlled. Others view the lower sensitivity as an advantage, as some individuals who receive positive PCR test results are infected but no longer capable of spreading the virus. As a result, antigen tests may shift the emphasis to identifying the most infectious individuals.
While antigen tests are now given by skilled specialists, several businesses are developing versions that are easy enough to conduct at home — similar to pregnancy tests.
“Speeding up, lowering the cost, and simplifying the rapid antigen tests is unquestionably the aim — and I believe the antigen test is the method to do that,” says Martin Burke, a chemist at the University of Illinois at Urbana-Champaign who is co-developing quick diagnostics, including antigen-based assays. “This is by no means the ideal option; it is just the quickest way to get started at the moment,” he explains.
What kind of rapid antigen tests are available and how do they work?
COVID-19 testing is classified into two types: diagnostic rapid antigen tests such as polymerase chain reaction (PCR) and antigen assays that identify components of the SARS-CoV-2 virus, and antibody rapid antigen tests that detect molecules produced by infected individuals. Antibodies form many days after infection and often remain in the blood for weeks after recovery, making antibody testing ineffective for diagnosis (see ‘Catching COVID-19’).
When given appropriately, high-sensitivity polymerase chain reaction (PCR) rapid antigen tests are almost 100 percent accurate in detecting infected individuals. However, such rapid antigen tests often need experienced workers, specialized reagents, and costly machinery that take hours to complete.
While countries such as South Korea and New Zealand have increased PCR-based testing, scaling these rapid antigen tests up has proven problematic in other countries. For example, the United States has experienced a sluggish and poorly organized response to outbreaks, as well as inaccurate testing from the Centers for Disease Control and Prevention (CDC) and supply chain issues. All of this has hampered attempts to collect and prepare samples for PCR, resulting in days or even weeks of waiting periods. These delays, along with a dearth of testing, have aided in the rapid spread of COVID-19 throughout the nation, which had claimed about 200,000 lives by 16 September.
A normal antigen test begins with a health care provider swabbing the back of the patient’s nose or throat — but firms are creating kits that gather saliva samples, which are simpler and safer to obtain than a swab. The sample is then incubated in a solution that ruptures the virus and liberates certain viral proteins. The mixture is then put to a paper strip coated with an antibody specific for these proteins, which are present in the solution. Positive test results are shown by a bright light or a dark band on the paper strip.
Rapid antigen tests provide findings in less than 30 minutes, do not need laboratory processing, and are inexpensive to make. However, such speed comes at a cost in terms of sensitivity. While a standard PCR test may identify a single molecule of RNA in a microlitre of the solution, antigen assays need hundreds — if not tens of thousands — of virus particles per microlitre to get a positive result. As a consequence, if a person has very low virus levels in their body, the test may provide a false-negative result.
When used on individuals who tested positive for SARS-CoV-2 by a routine PCR test, Abbott’s antigen assay detected the virus in 95–100% of cases when samples were taken within a week of the beginning of symptoms. However, this percentage decreased to 75% when samples were obtained more than a week after individuals initially manifested symptoms. The sensitivity — or percentage of accurately identifying infections — of the other antigen tests used in the United States ranges between 84 and 98 percent when a person is tested within a week of exhibiting symptoms.
Other rapid antigen tests that are quicker, cheaper, and more user-friendly than typical PCR assays are also being developed by companies and university research institutes, however they are not being commercialized on the same scale as antigen testing. Several of these additional assays use the gene-editing technique CRISPR to isolate coronavirus genomic bits. Others are faster variations of the PCR test that do not need the same chemicals, which means they are not constrained by the same supply-chain issues. For example, saliva-based polymerase chain reaction (PCR) assays are employed as screening techniques at colleges and by professional basketball teams.
How can you combat something you cannot see or feel? How do you approach it if you have no prior knowledge of it? These are only some of the concerns that the medical community worldwide was forced to address in days and weeks, rather than months and years, as a result of Covid-19’s fast proliferation. What is the first and most reasonable step? Social isolation, and – in many locations – government-mandated lockdowns to assist in containing the virus’s spread. It was followed by the development of successful rapid antigen tests methods, as well as the identification and documentation of novel symptoms, variations, and therapies. Learn more about rapid antigen tests by clicking here
This was all done alongside hastily performed clinical trials of vaccinations to aid in controlling the virus’s spread and effectiveness.
While all of these processes and tactics have had some success, one of the most efficient means of slowing the transmission of the virus – and finally eradicating it – was to develop a method of rapid antigen tests that was cost-effective, globally accessible, readily administered, and yielded speedy results.
This is the mechanism of action of the do-it-yourself Covid-19 rapid antigen tests.
It indicates if a person is contaminated or not, allowing them to isolate and be tested further. Since it is less expensive, faster, and more accessible than the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) test – which provides a definitive diagnosis – it is also an excellent method for isolating potentially large groups of vulnerable or sick individuals from the healthy population.
It is potentially lifesaving when you consider that the turnaround time for the RT-PCR test is between 24 and 72 hours on average, with greater delays recorded in certain places owing to surges or shortages.
With respect to COVID-19 cases again With the prevalence of HIV testing increasing throughout the nation and more individuals being tested, it’s important to understand the many kinds of tests available, since not everyone gets the same sort of test.
Understanding the many kinds of tests used to diagnose COVID-19 is critical to comprehending your results: how the test works, the possibility of a false negative or positive result, and your individual symptomatic chronology.
We met with pathologist Brian Rubin, MD, PhD, to get a better understanding of how these tests function and their primary distinctions.
Which COVID-19 tests are available?
There are now two basic kinds of COVID-19 rapid antigen tests available: molecular tests (also known as nucleic acid, RNA, or polymerase chain reaction tests) and rapid antigen tests.
The third form of rapid antigen tests looks for antibodies that have been produced in response to the infection. While these tests are sometimes utilized, they can only determine whether you have had the virus in the past. Additionally, antibody tests continue to confront concerns about their accuracy, the variability of antibody levels across patients, and whether or not findings are genuinely beneficial for general patients.
COVID-19 molecular assays
According to Dr. Rubin, molecular COVID-19 rapid antigen tests are “more sensitive and specific” than rapid antigen tests, making them more accurate. They are often conducted using a swab of a nasal specimen collected from the patient.
“What molecular diagnostics do is search for and identify the virus’s RNA (or nucleic acid),” Dr. Rubin explains. “This is in contrast to antigen testing, which seek for viral proteins.”
What is a polymerase chain reaction (PCR) COVID-19 test?
You’ve likely heard of polymerase chain reaction (PCR) rapid antigen tests, which are the most often used COVID-19 assays and a subset of molecular diagnostics, he continues. However, what is a PCR test?
To begin, the term “PCR” refers to the polymerase chain reaction, a technique for multiplying the nucleic acids in your sample. The polymerase chain reaction, according to the FDA, transforms any viral RNA in your sample to DNA and “amplifies” it by creating millions of copies of the DNA that the molecular test can identify.
Due to the fact that a PCR test can do numerous cycles of this amplification, it is capable of identifying the virus even if the viral RNA concentration in your sample is very low. know more about RAN at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2760750/
“Because there is little RNA in the samples obtained from your swab,” Dr. Rubin explains, “amplification enables laboratories to identify the virus more quickly and makes it more sensitive.”
What is the multiplex polymerase chain reaction (PCR) test?
RT-PCR rapid antigen tests have been the most frequently utilized kind of PCR tests so far in the pandemic. These assays are directed against a highly specific RNA. In this instance, the RT-PCR techniques are used to detect COVID-19 RNA.
Since the pandemic’s inception, however, specialists have created the Multiplex Assay PCR test, a more efficient PCR method capable of concurrently detecting for several viruses — COVID-19, influenza A, influenza B, and respiratory syncytial virus (RSV).
The CDC will phase out earlier RT-PCR tests in favor of the Multiplex Assay PCR test beginning in the winter of 2021-2022. Apart from being more efficient, it should aid in determining which virus patients are infected with, since the symptoms of different viruses may be very similar.
Which COVID-19 test is the most precise?
According to Dr. Rubin, the molecular COVID-19 test is more accurate than the antigen test. The trade-off is that although the majority of molecular tests return answers within 24 hours, some may take longer depending on whether they are transferred to an external laboratory and how busy that facility is with other rapid antigen tests.
That is the benefit of antigen tests: they may provide findings in as little as 15 minutes, do not need laboratory analysis, and have shown to be far less expensive to manufacture. Additionally, they can identify the virus in people who are still highly infectious, which aids in isolation and quarantine.
However, since antigen tests are less sensitive than molecular testing, a patient is more likely to have erroneously negative findings. False-negative findings are more likely to arise if someone is tested a week or more after beginning to have symptoms. At that moment, the quantity of antigen is often negligible and may go undiagnosed, despite the patient’s COVID-19 infection.
And, as more of these rapid antigen tests are performed at the point of care, where everything can be handled on-site rather than sent to a lab, they also require a better understanding of the results, other contextual information (such as the average positivity rate in a patient’s geographic area), and the potential complications associated with a false test result.
As a result, for the time being, PCR tests remain the gold standard for COVID-19 rapid antigen tests.