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What is PCR Test?

The ongoing pandemic is caused by the Coronavirus that is life-threatneing. The Novel Corona Virus was initially identified in the city of Wuhan, China in December 2019. Hence the name COVID-19. The the virus has spread tremendously, thereafter. In this article, we will learn about what are the symptoms of Coronoa virus, how to identify them, precautions to be taken, and the procedure of the PCR test.

PCR full form is Polymerase Chain Reaction. It is a type of test that aims are identifying the genetic material of a particular organism, especially viruses. The presence or absence of the virus can be detected through this test. Sometimes even though the virus gets into the person’s body the symptoms are not found, as the person has high immunity. Undergoing this test can help us in detecting the presence of fragments of the virus. PCR can be done in several different ways based on the type of virus that infects the body.


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Types of PCR

There are different types of PCR to detect different types of viruses. 

  • Amplified fragment length polymorphism PCR (AFLP)

  • Allele-specific PCR

  • Alu PCR

  • Assembly PCR

  • Asymmetric PCR

  • COLD PCR

  • Colony PCR

  • Conventional PCR

  • Digital PCR (dPCR)

  • Fast-cycling PCR

  • High-fidelity PCR

  • High-Resolution Melt PCR (HRM-PCR)

  • Hot-start PCR

  • In situ PCR

  • Intersequence-specific PCR (ISSR-PCR)

  • Inverse PCR

  • Linear after the exponential PCR (LATE-PCR)

  • Ligation-mediated PCR

  • Long-range PCR

  • Methylation-specific PCR (MSP)

  • Miniprimer PCR

  • Multiplex-PCR

  • Nanoparticle-Assisted PCR (nanoPCR)

  • Nested PCR

  • Overlap extension PCR

  • Real-Time PCR (quantitative PCR or qPCR)

  • Repetitive sequence-based PCR

  • Reverse-Transcriptase (RT-PCR)

  • Reverse-Transcriptase Real-Time PCR (RT-qPCR)

  • RNase H-dependent PCR (rhPCR)

  • Single-cell PCR

  • Single Specific Primer-PCR (SSP-PCR)

  • Solid-phase PCR

  • Suicide PCR

  • Thermal asymmetric interlaced PCR (TAIL-PCR)

  • Touch down PCR (TD-PCR)

  • Variable Number of Tandem Repeats (VNTR) PCR

Among the above-mentioned types, the one which is used to detect COVID-19 is the RT-PCR test. In order to detect the coronavirus, the RT PCR test procedure is mentioned below. PCR is a molecular technique used to analyze the upper respiratory specimen. It is done to identify the genetic material, RNA of the SARS-Cov-2 virus that causes COVID-19. Where the small amounts of genetic material, RNA are taken from the samples and amplified into DNA. Thus the amplified DNA is replicated till the SARS-Cov-2 virus is found if it is present in the specimen. The PCR test is the gold standard test that is used to diagnose COVID-19. It was authorized to use in February 2020, it is more reliable and accurate. 


Symptoms of COVID - 19

The doctors may suggest to undergo PCR procedure if they find the below-mentioned symptoms in the person. 

  • Cough

  • Rise in body temperature or chills 

  • Difficulty in breathing or shortness of breath

  • Body and headache

  • Loss of smell or taste

  • Runny nose or congestion

  • Vomiting or nausea

  • Diarrhoea

  • Sore throat

But these symptoms are either present or absent in the person even though they have been infected with the virus. There are chances that people might not develop all the symptoms mentioned above. In such cases, the under going the test to detect the virus is most suggested. The types of tests include PCR test, Lateral flow test, an antibody or antigen test. The antibody test decides if the person has immunity to the virus. Whereas, the antigen test detects the presence of proteins of the virus.


PCR Technique

The test for COVID-19 is done in three following steps.

  1. Collection of Samples: The respiratory material in the nose is collected using a swab. Where swab is a flexible stick that has a soft tip. There are different types of swabs, nasal swab is the one that is used to collect the sample in the nostrils. Nasopharyngeal swabs are used to collect samples in the nasal cavity. Both types of swabs are sufficient to collect the specimens. They are sealed further and are sent to the laboratories for tests.

  2. Extraction: The process of extraction or isolation is done by the scientists in the laboratory. The genetic material of the sample is isolated from the rest of the sample.

  3. PCR: In the PCR steps, the chemicals and special enzymes along with a PCR machine called a thermal cycler is used. In the thermal cycler, the heating and cooling cycles are used to increase or amplify the genetic material. Later the numerous copies of the genetic material are produced after many cycles of heating and cooling. Then the special chemicals used in this procedure produce fluorescent light if the SARS-CoV-2 is detected in the sample. Once the material is amplified more than sufficient and if the signal is produced then it is detected by the PCR machine. This interpreted signal is used by the scientists to find the result as positive. If the signal is not produced then the test result is considered to be negative.

  • The positive test result means that the person is been infected with the SARS-CoV-2 virus. In the case of asymptomatic infection, it is considered to be the SARS-CoV-2 virus. If the symptoms are found then it is COVID-19. A person with mild illness can be recovered by taking certain medications from home. If the symptoms are worsening then it is suggested to contact a healthcare provider.

  • The negative result means that the person is not infected with the virus.

However, it is always suggested to take certain precautions to prevent getting infected with the virus and to break the spread of the virus.


Precautions

As the proverb says “Prevention is better than cure”, it is suggested to take certain measures in order to stop the rapid spreading of the deadly virus.

  • Maintaining the social distancing, at least a one-meter distance is to be maintained from people even if they don’t seem to be sick.

  • Staying indoors is the best way to avoid getting infected.

  • Maintaining hygiene is suggested, washing your hands, being in a well-ventilated area, etc.

  • Covering your mouth while sneezing or coughing.

  • Wearing a mask that covers mouth and nose while reaching public places.


The difference between the types of tests are given below,

Difference Between PCR Test and Antigen Tests

PCR Test

Antigen Test

This test is done to find the presence of the genetic material of the virus or its fragments if it is broken down. 

This detects bits of proteins on the surface of the virus called antigens. 

PCR is considered to be the most reliable and accurate test for detecting active infection. 

Rapid antigen tests are found to be most accurate when it is used within a few days of the start of the symptoms, when the virus in the largest amounts is present in your body.

PCR tests can take hours to perform.

Antigen tests can typically take about 15 to 30 minutes.


The term COVID-19 or Novel coronavirus is the majorly heard word nowadays. It is a deadly virus that either affects directly or indirectly the lives of people. It could be prevented only when each and every person put effort into following the instructions provided. Maintaining the proper diet, following regular exercise routines, and developing the immune system to fight against the virus is considered the best way.

FAQs (Frequently Asked Questions)

1. What is PCR and mention its full form?

PCR full form is Polymerase Chain Reaction. It is a technique that is been used to amplify the specific target DNA sequence. Thereby allowing the occurrence of the process of isolation, sequencing, or cloning of a piece of the sample or single sequence among many.

2. Mention the uses of PCR.

The polymerase chain reaction or PCR has been elaborated in various ways since its introduction. Common PCR uses for a wide variety of applications include:


  • Genotyping

  • Cloning

  • Detection of mutations

  • Sequencing

  • Microarrays

  • Forensics

  • Paternity testing

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