Introduction
Since the outbreak of the Coronavirus (commonly referred to as COVID-19), the persistence of understanding virology and developing methods to identify its presence in our body was a component that led us to slowly recover from the pandemic. COVID-19 tests, such as the NAATs and the Antigen Test, are viral tests that detect an infection with SARS-CoV-2, the virus that causes COVID-19. A viral test is a diagnostic test which helps detect a viral infection in the body. Viral tests like these are what helps us identify infected individuals which can prevent the spread of the infection.
Diagnostic Methods
Virological tests aims to serve the following:
Detection of viral particles
Analysis of the viral components
Identify the cytopathological effects (CPE): the change of cell morphology due to the infecting virus
Evaluation of the patient’s antibody response to the virus
Although it is a process which consumes time and money, laboratory testing is required for the confirmation of the pathogen’s identity and its presence in the body. The verification helps us determine which type of treatment the patient needs according to the results of the diagnosis. Yet, deciding which assay is most suitable for each case can be daunting (Kennedy M., 2005). An assay is an examination to determine the specific characteristics of a substance.
Virus Detection
According to Kennedy, there are several methods that can be used when detecting a virus:
Viral propagation
Visualization using electron microscopy
Protein detection
Nucleic acid detection
Viral activity detection
Virus Isolation
It is a very specific method for diagnosis of viral infection, yet present methods are time consuming and expensive (Morley, P. S., & Pusterla, N.,2014; O’Neill et al., 1996). But, it is more sensitive than the antigen detection assays. Virus isolation is an assay which allows any virus present in the sample to be propagated, hence, a nonspecific assay. Samples are usually collected from disease lesions using swabs, fluids, and tissue samples. Collecting samples for virus isolation is ideally done during the acute phase, sudden onset or development of symptoms (Kennedy M., 2005).
Electron Microscopy
It is a technique which enables visualization of the virus through producing high resolution images from the sample. It is the oldest method for direct visualization of the virus, and presently, it is mostly used for research rather than diagnostics (Upadhyay, S., 2023). Electron microscopy, like virus isolation, is also a nonspecific assay. Equipment required for this technique is only limited to academic and research institutions since it is costly and needs high maintenance.
Antigen Detection
An antigen is a substance which triggers an immune response from the body since the immune system does not recognize it. In an antigen test, antigens are detected from a sample taken from the body. These antigens could be the proteins that make up a virus, such as with SARS-CoV-2, the virus which causes COVID-19 (Geng, C., 2022). Antigen tests produce rapid results, though more sensitive results are obtained by the gene detection method, PCR, another laboratory technique used to test COVID-19 (Grandien M., 1996).
References
Kennedy M. (2005). Methodology in diagnostic virology. The veterinary clinics of North America. Exotic animal practice, 8(1), 7–26. https://doi.org/10.1016/j.cvex.2004.09.009
Morley, P. S., & Pusterla, N. (2014). Equine Sports Medicine and Surgery (2nd ed., pp. Pages649-664). Saunders Ltd. https://doi.org/10.1016/B978-0-7020-4771-8.00030-2
O'Neill, H. J., Russell, J. D., Wyatt, D. E., McCaughey, C., & Coyle, P. V. (1996). Isolation of viruses from clinical specimens in microtitre plates with cells inoculated in suspension. Journal of virological methods, 62(2), 169–178. https://doi.org/10.1016/s0166-0934(96)02102-7
Upadhyay, S. (2023). Viral Infections and Antiviral Therapies (pp. Pages99-120). Academic Press. https://doi.org/10.1016/B978-0-323-91814-5.00003-9.
Geng, C. (2022, March 24). What to know about antigen tests. Medicalnewstoday.com. https://www.medicalnewstoday.com/articles/what-is-an-antigen-test
Grandien M. (1996). Viral diagnosis by antigen detection techniques. Clinical and diagnostic virology, 5(2-3), 81–90. https://doi.org/10.1016/0928-0197(96)00209-7
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