Fighting Coronavirus: US regulator approves “saliva based” Covid-test kits; Check how they work

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August 20, 2020 3:35 PM

The developers of saliva based test kits have also claimed that in over 90% of the cases, health workers will not need to wear PPE suits while collecting the samples resulting in further reduction of the cost.

The U.S regulator also termed the development groundbreaking as it could quicken the testing and tracing of the patients contracted with the virus.The U.S regulator also termed the development groundbreaking as it could quicken the testing and tracing of the patients contracted with the virus.

Even as many vaccine candidates are in different stages of human trials, scientists on the other spectrum are also devising ways to test and trace Covid-19 among large populations. In a recent development, the US Food and Drug Administration (FDA) approved a new testing method for Covid-19 called Saliva test. The U.S regulator also termed the development groundbreaking as it could quicken the testing and tracing of the patients contracted with the virus. A similar Saliva test kit has also been developed by Israel’s Center for Geographic Medicine and Tropical Diseases which has been claimed to provide its test results in less than a second. However, the kit developed in Israel has not been approved by the regulator yet, according to an Indian Express report.

What is a saliva test?
Presently the two most prevalent testing methods for Covid-19 are the RT-PCR test that is conducted by collecting the swabs from the patient’s nose and throat and antigen test that tests the blood samples of the patient. The low cost saliva test which has been developed by the researchers will only require the patients to spit into a sterile tube and the sample of the saliva is then sent to the laboratory. In the last few months, more than five saliva based tests have been authorised to be used by the US regulator FDA.

What are the advantages of the Saliva test?
The developers of the saliva based test kit have highlighted the biggest advantage of saliva based testing method is the ease of collecting the samples and less economic cost in comparison with the RT-PCR tests. While a skilled health worker and a certified swab and collection receptacle are needed to collect the sample in RT-PCR test, saliva samples can be collected even by unskilled health workers which would cut the cost of conducting tests.

The testing method has also been claimed to be more accurate than the RT-PCR tests as the swab based tests may result in false negatives. Apart from cost and accuracy, the saliva based test can drive away the phobia among people of letting the swab deep inside their throat and nose. Chances of infection from patients to the healthcare worker collecting the samples would also substantially reduce. The developers of saliva based test kits have also claimed that in over 90% of the cases, health workers will not need to wear PPE suits while collecting the samples resulting in further reduction of the cost. Travelling to a laboratory and hospital to get tested would also be curtailed as the tests can be conducted from any space.

What is the scientific procedure adopted by saliva test?
Like the RT-PCR test, the saliva test also converts the virus RNA into DNA before amplifying the DNA to detect the presence of the virus. Yale School of Public Health which has developed a kit based on saliva testing method has also done away with a separate step which was used to extract the virus RNA. The test kit developed by the Yale school does not require saliva collection tubes containing preservatives and neither does it need equipment for nucleic acid extraction, according to the study quoted in the report.

Are there any limitations of the saliva test?
Like every Covid-19 test, the saliva test also has its own limitations. The Yale researchers have said that the presence of blood and mucus in the saliva of patients might interfere with the testing process and might give false results. The US regulator also cautioned that apart from the test results provided by the test kits, clinical behaviour of the patient including symptoms, patient history, epidemiological information must also be analysed to reach on any conclusion. It also said that to avoid a probable case of a false negative, other specimens must be tested before the final confirmation.

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