Polymerase Chain Reaction (PCR) Tests
The emergence of the COVID19, during early 2019 in China, posed a significant threat to the whole globe, considered just yet to be the greatest pandemic of the century. The countries all over have been given a catastrophic blow by the pandemic, prompting to the application of the previously known risk-assessment tools as a combat factor. The method has shown futile to the pandemic since it has been yet approval that the virus has evolved from its original attack back in 2011. The scientists have been indulged to come up with ways of detecting the virus more adequately, like the recently tried-and-true polymerase chain reaction (PCR) although other methods are coming up.
According to NCBI, PCR or Polymerase Chain Reaction is a revolutionary method used to make billions of copies of specific DNA samples in medical and biological research labs, developed by Kary Mullis in the 1980s. PCR is an old technology behind the various microbial detection processes like malaria, HIV, COVID19, hepatitis, among others. PCR technology is known for its ability to detect the slow antimicrobial growth of organisms at the early stages. The use of PCR technology enables early diagnosis of the novel coronavirus and has proven to be active so far.
PCR tests for COVID19, start withdrawing of mucus from the patient’s nasal cavity using a nasopharyngeal swab, resembling a long Q-tip. (Reardon, 2020) These swabs are placed into vials and transported into an FDA-approved central lab facility for testing. Several reagents are used by the technicians to extract any viral RNA within the samples. Transcriptase enzyme is used to convert the extracted RNA to a complementary sequence of DNA. The DNA sequence can then be replicated many times over to make it easy for the detection process. At times, the replication process is accelerated by additional reagents that comprise pairs of primers containing copies of pieces of the DNA matched to the COVID19 genetic code.
The PCR technology would not be complete without the PCR machine that regulates temperature conditions during the process. The machine raises the temperature during the process to lead to the separation of the two strands of DNA helixes into single strands. Temperatures are lowered to enable the primers and reporter strands to bind to the corresponding sequences of single strands. The polymerase enzyme is added to latch the premier bound to the DNA strand, at intermediate temperature levels. The results of the process produce a fluorescent probe release at the reporter sequence showing the strand was copied. The process is then repeated consecutively for around 40 cycles to create an optimum 100 billion copies of the targeted DNA and the fluorescent signal.
According to Steven Wolinsky, the whole process has proven quite accurate and selective, known to correctly to discern the positive and negative cases but there are some slight drawbacks. Statistics have shown that 67% of the patients normally test negative at early stages of infection, say 0 to 4 days while 38% per cent of the patients are negative on the first day of the symptoms. Several countries like Russia that has implemented the method, reported in their South Korean CDC (Park, 2020) that some cases the individuals are also able to recover but still poses few traces of the COVID19 virus, but pose no threat to be spread to other hosts.
The PCR test is just among the best ways to test the COVID19, but due to its certain setbacks other methods like the antibody tests should be implemented along to increase efficiency as other more apt ways of testing are brew.
References
Reardon, C. (2015). Guidelines for Designing Real-Time PCR Experiments.
Park SY, Kim YM, Yi S, Lee S, Na BJ, Kim CB, et al. (2020) Coronavirus disease outbreak in the call centre, South Korea.
Emerg Infect Dis.