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After 7 months COVID 19 hitting the world, there are few COVID 19 screening test that has been produced to help the frontline in diagnosing patients. According to the WHO and CDC, the gold standard for diagnostic molecular testing for COVID 19 in Malaysia is the RT-PCR technology due to it is capable of detecting small amounts of pathogens, it is yet to be elucidated what positive result means among those who are asymptomatic. However, there are few disadvantages that can lead to false-negative results which is the timing of conducting the tests, hence, the doctors need to use their clinical judgement even though the patient is negative by observing clinical signs, patient history and epidemiological information. Only trained clinical laboratory personnel can handle the RT-PCR test and strict biosafety precautions should be adhered to when handling human clinical specimens suspected to be COVID 19 infections.
In addition, the RT-PCR test only detects when an active virus is present, it cannot detect if a person has had the virus and then cleared it after the end of the COVID-19 disease. A negative result cannot rule out the disease yet because it could mean that the person is not currently infected by the virus, the sample taken was of poor quality, the virus is not present at the site the sample was taken from or that it is too early, or too late in the infection to detect replicating virus. Repeated new patient sample needs to be taken in a few days later if the result was negative on the first test. It is important to reduce the chance of incorrectly missing an infected person.
The procurement of expensive materials and equipment of RT-PCR test kit contains four reagents; three primer probes mix for targets virus nucleocapsid (N) gene for specific detection of SARS-CoV-2, targets virus nucleocapsid (N) gene for specific detection of SARS-CoV-2 and targets human RNase P gene for detection of human nucleic acids as a control for sample integrity. The last reagent is nCoVPC which is noninfectious positive control material that yields a positive result in each assay included in the panel. The materials include PCR reagents and items that are commonly used in clinical laboratories, such as a microfuge, microcentrifuge tubes, pipettes, pipette tips, etc, are not included with the test but they are required while performing the test. Two control materials that are used to provide expected results for a test to be considered valid are also required but not provided.
The process of these assays take 1 to 3 hours to perform and somehow, it can take upwards of 24 hours if the local lab does not have molecular testing capabilities in-house. The test kit enzymes in RT-PCR copy the RNA to DNA, which is amplified to allow virus detection by using a PCR machine which cycles the test temperature so that roughly 35 billion copies of viral DNA are made for each viral RNA strand that was originally present after any proteins, fats and other molecules being removed by chemicals and leaving the only RNA behind. Then, the enzymes copy Fluorescent markers which are used to bind to the amplified DNA and produce light. A special machine is needed to read the light in order to produce the test result. The machine will show the positive result if the intensity of the light produced within the sample reaches a certain threshold.
Other than RT-PCR, there are many available diagnostic tests for COVID 19 now. These tests are largely based on the other three different techniques which are loop-mediated isothermal amplification (LAMP), lateral flow and enzyme-linked immunosorbent assay (ELISA). LAMP is a simple test, however, the testing method is less developed yet. Lateral flow or Colloidal Gold Immunochromatography is handheld single-use assays which provide results for an individual patient in 15 minutes. Lastly, ELISA is a quick and technically simple assay. It can be easily read and offer relatively high throughput.
