Testing is proving one of the essential components in the fight against COVID-19 and testing capabilities have come along in leaps and bounds since the pandemic was declared in March 2020. Rapid molecular and antigen diagnostic tests for COVID-19 are now being used in many locations to provide faster, cheaper and more accessible results, without needing to send samples to a lab – typically in 10 to 15 minutes. However, several recent events have highlighted how important it is that these tests are used and interpreted correctly.
What are the concerns?
In the UK: Early November of 2020 saw doubts raised about the UK’s plan to roll out 20 million rapid antigen COVID-19 tests, also known as lateral flow tests, for use in community testing. Although the government has stressed that the tests will be appropriate, there are two important considerations for the use of these rapid tests:
- The tests are specified to be performed by healthcare professionals, not by the general community.
- The tests are specified for testing in people who have symptoms of COVID-19, not for asymptomatic testing.
The particular test that the UK plans to use, made by Innova, was shown in three different trials to have varying results based on who completed the test. The Innova lateral test detected 79.2% of active COVID-19 cases when carried out by laboratory scientists; 73% when carried out by healthcare professionals; and only 58% of active cases when carried out by self-trained members of the public. One concern is that these tests might be performed by those who aren’t qualified to do so.
The other concern is that people with low viral loads (who may be largely asymptomatic) may not show a positive result, leading to a false sense of security that the person is COVID-free. Given an estimated 40-45% of people with SARS-CoV-2 infection are asymptomatic but can still transmit the virus to others, this could lead to uncertainty in key environments. Several studies of lateral flow tests have also demonstrated a 0.32% false positive rate. While this rate is low, the concern is that this could produce false positives across large populations.
In the US: The rapid testing issue has also been linked to the White House. News outlets have discussed the fact that the Trump administration was regularly using Abbott’s rapid molecular ID NOW (and later antigen BinaxNOW) tests to screen people who were to be in close contact with the president, which may have led to a false sense of security. President Trump, the First Lady and a handful of administration officials tested positive for the virus in early October 2020. Elon Musk also made headlines in November after tweeting sceptically about taking four of Becton Dickinson’s rapid antigen tests and receiving two negative and two positive findings. As Andy Pekosz, a professor of microbiology at Johns Hopkins University told the Los Angeles Times, it was likely that Musk could have been at the start or end of an infection with a barely detectable amount of virus in his system that might have led to inconclusive results.
The US government has recently purchased millions of the Abbott BinaxNOW tests to distribute to vulnerable communities around the country. According to the FDA’s official procedure for the test, the antigen is generally detectable in nasal swabs during the acute phase of infection in the first 7 days of infection, and the test should be carried out by a healthcare provider. The documentation outlines that ‘Negative results do not rule out SARS-CoV-2 infection and should not be used as the sole basis for treatment or patient management decisions, including infection control decisions’.
The FDA has also released a letter that warns false positives can occur with antigen tests, and reinforces that ‘health care providers and clinical laboratory staff can help ensure accurate reporting of test results by following the authorized instructions’.
How is Point of Care testing being carried out?
There are several different types of tests being used at point of care settings, where tests are administered at or close to the point of healthcare.
- Diagnostic tests
Diagnostic tests are designed to show whether someone has an active coronavirus infection. These include:
- Antigen tests, which detect specific proteins from the virus. There are several antigen tests available and being trialled, and each offers different sensitivity, specificity and recommendations for use. Most of the rapid testing options are antigen tests, and due to their poorer sensitivity are appropriate only for acute infections or those showing symptoms of COVID-19 who tend to have a higher viral load. Most require a nasal or nasalpharyngeal swab.
- Molecular tests, which detect the virus’s genetic material. This includes real time PCR or RT-qPCR tests, which are currently the gold standard in COVID-19 testing because of their high sensitivity and specificity. Most molecular tests use a nasopharyngeal, nasal or throat swab, while some can use a saliva sample. Rapid molecular tests have a shorter thermal cycling process compared to the complete PCR assay, and as such tend to have lower sensitivity and a higher chance of false negatives.
- Antibody tests, which detect antibodies to the SARS-CoV-2 virus. This type of test is taken through a serological (blood) test, and indicates whether someone is recovering from or has had the virus. As antibodies can take days or weeks to develop in response to the virus, antibody testing isn’t suitable for diagnosing active infections.
So – is there a place for rapid testing for COVID-19?
There absolutely is. Rapid testing can offer speed, affordability and accessibility benefits over PCR testing, which can require robust systems to be put in place. PCR testing can require lab space, time for the assay and logistics to get samples transported correctly. Even some developed countries have experienced difficulties in rolling out PCR testing for COVID-19 effectively – not to mention low-income countries that can benefit greatly from having access to rapid testing. Some information is better than no information, after all. And rapid testing will be able to capture most highly contagious infections in people with high viral loads.
However, there’s an important balance to find between easy testing and the accuracy of testing.
Balancing speed and access, with accuracy
Speed is no doubt going to be of the essence when it comes to testing for COVID-19 in healthcare settings, border points, airports, workplaces and even more so as travel opens up over time. Any possibility of testing more people with fewer resources can be useful in this new global era of outbreaks and infection control.
That being said, it’s essential to act with the knowledge that real time PCR is still the gold standard in testing for COVID-19, and that rapid tests should be supported by confirmatory PCR testing wherever possible. Understanding the sensitivity, specificity and suitable purpose of these rapid tests is going to be key in effective public health management.
Bio Molecular Systems’ Mic qPCR instrument is designed to speed up the real time PCR testing process while optimising accuracy. The robust yet compact design of Mic means that these instruments can be easily transported for use at the point of need. Mic’s sample throughput is also much higher than most point of care devices at 48 samples per run, which allows for large numbers of COVID-19 tests to be performed quickly at the point of need with the same sensitivity as the gold standard lab-based test. The fact that Mic requires minimal maintenance and no servicing or calibration means that it’s as ideal for use in remote locations as it is in centralised labs. Tests should be run under the supervision of qualified technicians, such as those who will be employed at airports and other on-the-spot testing venues.
Here are just some of the locations where Mic is in use for COVID-19:
- Mic units have now been included in over 120 COVID-19 testing packs sent worldwide by the Atomic Energy Agency (IAEA), in a project funded by Takeda Pharmaceuticals.
- The Czech Army is using Mic together with a range of other equipment in their mobile laboratories. These labs are vehicle-based and can be relocated to wherever a rapid response is needed, such as testing a specific population or workplace.
- Indonesia has placed over 75 Mic units into regional COVID-19 detection labs, to enable rapid testing in remote areas of the country.
- Mic units are being used throughout Turkey, including at COVID-19 centres in state hospitals; genetic laboratories at key airports; Turkey’s presidential palace health centre in Ankara; and by R&D companies developing COVID-19 RTPCR kits.
- Several hundred Mic units have been sent to China where Liferiver Biotech has CFDA approval to sell Mic as a medical device in China, along with their COVID-19 detection kits.
- The Philippines now has over 40 Mics in place for COVID-19 detection. And,
- The Western Australian Government is using Mic at border checkpoints.
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