Saliva test

Subject: Science and tech

Context:

US Food and Drug Administration (FDA) approved a new method of testing for Covid-19 by processing saliva samples

Concept:

• The inexpensive test called Saliva Direct has high sensitivity and can detect the virus even when the number of virus copies in the saliva sample is as low as 6-12 copies per microlitre.
• Collecting and testing saliva samples involves three steps collecting saliva without preservative buffers, proteinase K treatment and heat inactivation, and dualplex RT-qPCR virus detection.

Significance:

• The new saliva test would increase efficiency and avoid shortage of crucial test components such as reagents.
• The new test makes sample collection non-invasive and reduces the need for trained healthcare workers to collect the samples, reducing the risk of infection during collection.
• In contrast, tests using nasopharyngeal swabs lead to false negative results due to errors at the time of sample collection.

Testing methods:

• Broadly, there are two types of tests for Covid-19.
• One type, which detects the virus itself, includes the RT-PCR test and the antigen test.
• The second is the serological test, which looks for antibodies developed by the body against the virus. This determines if a person has been exposed to the infection, and is used for surveillance of infection in a community.
• In the first category of tests, nose and throat swabs are used as the sampling technique .
• After the swab is removed, the sample is placed in a viral transport media and is preserved for analysis.
• Researchers have developed the saliva test as a low-cost alternative; the suspected patient has only to spit into a sterile tube and the sample is then sent it to the laboratory.