As Covid-19 continues spreading all over the world, depleting reagents and resources needed for testing, alternative methods of testing are being sought to aid the process of detecting the infection. Rapid test kits, which are said to give results within minutes, are being discussed in Thailand, especially after Chulalongkorn University announced that it has developed its own serology-based test kits and is open for people to receive the test.
However, it should be noted that these test kits come with their own limitations. The results they yield may not be the simple "negative" or "positive" people look for.
The main method that is being used to test the presence of Sars-CoV-2 or the novel coronavirus is RT-PCR, which is considered a direct diagnosis to determine active cases of patients who are infected, as well as their ability to spread it. Samples can be gathered through nasopharyngeal and a throat swab. This is considered the most accurate method of testing for Covid-19 today. However, it takes around one-and-a-half to two hours to get results.
With the infection spreading wider, scientists and medical professionals are looking into an "indirect" alternative, which is the serology test that detects IgM and IgG antibodies that are produced in response to the infection. It can be done by putting a blood sample onto a strip of the rapid test kit, where coloured bans will appear to show if there's a presence of antibodies. This takes about 15-20 minutes for results to appear.
However, it should be noted that the results of the RT-PCR and serology tests can't be interpreted the same way.
A view shows rapid tests for coronavirus as medical specialists collect blood specimens of employees of local municipal institutions in Lviv, Ukraine. (Photo: Reuters)
"Currently, we mostly pay attention to whether a person is infected with Covid-19 or not. However, with the serology test, even if the result comes up as positive, it may not mean that a person is infected. It could also mean that they have been infected unknowingly for a while and that the body has produced antibodies, meaning they have an immunity but are asymptomatic," said Patcharaporn Boonyos, medical scientist in virology from Thailand-Japan Research Collaboration Center on Emerging and Re-emerging Infections, a collaboration between Osaka University and the Ministry of Public Health in Thailand.
Most also jump to the conclusion that a negative result means they aren't infected with Covid-19, and this can be misleading.
"For the serology test, a negative result has two meanings. One, it could mean that you're not infected. Two, it could mean that you are infected but in an early stage wherein the body has yet to produce an antibody. This may lead to a false result, which could come up positive if you were to take the test again later.
"The US Food and Drug Administration [USFDA] has issued a warning that the serology test alone can't be used to conclude whether a patient is infected with the virus," added the scientist. "Even if a person's result shows negative, it's not recommended to let them go back to work or out into society like normal with no quarantine."
Chulalongkorn University's website says its serology-based Chula Covid-19 Strip Test doesn't serve as a replacement for the standard Covid-19 test, but hopes it can lessen the burden and traffic of patients at the hospital through this initial screening. Those interested in taking the serology test can register via an online application at covid19.thaitechstartup.org to screen their level of risk. People with medium to high risk may receive an appointment to get the test done.
The serology test has been used in medical facilities in various countries, including China, the United Kingdom, the United States and certain parts of Europe and Asia. As of now, test kits have yet to be developed for home diagnosis.
A Covid-19 rapid test kit at the World Health Laboratories in Bunnik, the Netherlands, after the laboratory received a trial shipment from China. (Photo: AFP)
What's worrying is that many people now express misled and misguided interest in these test kits, believing they can replace the more expensive RT-PCR at the hospital and think they can simply buy the kit and do the test themselves to find out if they're infected. Some have sought out these kits and resorted to dubious online sellers to get their hands on one.
Assoc Prof Jessada Denduangporipant from the Department of Biological Science, Chulalongkorn University's Faculty of Science, said that no test kit has yet been approved for public sale by Thailand's FDA and the Ministry of Public Health, hence they're illegal. Some online sellers have already been apprehended by the authorities.
"We never know if the test kits being sold online are genuine, up to standard, or if they're accurate at all. It is worrying because a wrong result can affect a person's life greatly. If they get a false positive, they may panic and rush to the hospital, increasing the already heavy workload experienced by healthcare professionals. And if it's a false negative, then it's even worse, because people may get careless with social distancing and spread the virus to others," said Jessada.
Both Jessada and Patcharaporn insisted on the test kits being administered by knowledgeable medical professionals only.
Patcharaporn also expressed her concern over waste management. Used kits, as well as used equipment such as alcohol pads and cotton, require proper disposal or they may be at risk of spreading diseases to the public.
"For the public, they don't need to seek out these kits for use at home. There are more pros than cons. The accuracy to the answer they are looking for is also low. If they really need a test now, then they should at least have certain symptoms to show that they may potentially be infected, like a fever. Then they could go and have a check-up," Jessada concluded.
Despite its limitations, the serology test does have several benefits. It can be used to track back and see how many people are actually infected within an area. This record can help predict the possible rate and extent of infection in the future, as well as hot spots where there is a high number of infections, in order to develop suitable preventive measures.
"If we don't know the exact number, we may underestimate the situation," said Patcharaporn.
Another benefit of the serology test is that it may be helpful in screening for potential antibody donors, as the antibody may be extracted and used to treat Covid-19 patients in severe conditions.
It could also be used in conjunction with the RT-PCR. If a person tests negative on the RT-PCR and positive on the serology test, then they are safe and can be sent back to work. This is suitable for healthcare workers who take care of infected patients, as it's determined that they have no virus but immunity against it.
"At the same time, it's currently unclear how long this antibody actually lasts. In some cases we see, people who have been infected can get reinfected in a few weeks. So, it's still unclear whether this immunity really works or if it can prevent us from reinfection or not," she said.
OVERALL SITUATION
So far, the world has almost 2 million confirmed cases of Covid-19, with more than 100,000 deaths. It was recently reported that only 6% of the actual infection is detected worldwide.
In Thailand, there are more than 2,500 confirmed cases, with about 40 deaths. The number of new infections has lowered recently, which Patcharaporn believes may be a combined result of people working more from home, closure of public venues, curfew, and the depleting reagent required for the test. It's also possible that infected people who are asymptomatic are staying at home.
Still, she added that this lowered number remains at about 10% of patients under investigation daily. The more these tests can be done, the faster those who are infected can be found.
"We now screen only those with apparent symptoms before they can get the RT-PCR done, meaning we may miss out on asymptomatic patients. It's difficult to test everyone, because there are simply not enough tests and resources, but at least we can expand it to cover those in risky groups, such as people who came back from abroad and workers whose jobs require them to meet a lot of other people, like bus, van and taxi drivers. This should also include overlooked jobs like garbage collectors and cleaners," said Patcharaporn.
"To ensure that fewer people are being infected, we'll have to look at it in the long term, like a month. We may see a surge in seven, 14 or 27 days after this. The time it takes for each person to develop symptoms is different," she said.
