Difference Between Serology Test and PCR

Despite medical advances in diagnostics and vaccinology, infectious diseases still have devastating effects on not only the human population but economies worldwide. Many infectious diseases can be considered emerging, re-emerging, or new, like the novel coronavirus. These are diseases caused by specific modifications of agents that are already present in the environment and they can evolve or mutate by changing conditions. In a fight against these infectious diseases, the quest for improved and advanced diagnostic methods has become even more important. The detection of pathogens through serology has played a major role in epidemiological research and studies. However, with the advances in molecular biology, the analysis of pathogens required new methods, such as the polymerase chain reaction (PCR) for more improved diagnostics.

What is Serology Test?

Serology test is a diagnosis test for infectious diseases through the use or detection of serum globulins, known as antibodies. It is a blood-based test that can detect if an individual has antibodies to a specific pathogen. However, antibodies are only half of the reactants in serology tests; they need something to react with, namely antigens. Serology basically refers to the study of serum. The diagnosis can be done by detection of an immunologic response specific to an infectious agent in an individual’s serum. This test looks for potential traces of pathogens in a person’s blood sample to determine whether or not that person has been exposed to the virus. For example, in case of COVID-19, many nations are testing for SARS-CoV-2 antibodies at the population level to keep track on the ongoing outbreak and study the extent of the outbreak.

What is PCR?

One of the most frequently used methods in molecular diagnostics is the polymerase chain reaction (PCR). PCR is an in vitro replication procedure that amplifies the target DNA. It is basically a method that amplifies a specific fragment of DNA in order to increase the target DNA to detectable levels. PCR looks directly for the genetic material of a virus in a nasal or throat swab. PCR basically makes millions to billions of copies of a particular segment of DNA. Human DNA is composed of two complementary strands that form a double helix. So, if you know the sequence of one strand, you can replicate the other half. PCR is typically a three-step process – the first step is called ‘denaturation’, which involves separating the two strands of a DNA sample apart; the second step is ‘annealing’, which specifies the region of DNA that will be copied; and the final step is ‘extension’, which copies the DNA.

Difference between Serology Test and PCR

Basics

 – So, what is serology testing? Serology is basically the scientific study of serum or plasma, particularly in response to the body’s immune system response. Serology test is a diagnosis for infectious diseases through the use or detection of serum globulins, known as antibodies. It helps identify if an individual has been exposed to a virus. Polymerase Chain Reaction, or PCR, is one of the most frequently used methods in molecular diagnostics that determines if a patient has an active infection. It gives a clean picture of the patient’s clinical status with regard to the virus.

Testing 

– Serology test is a diagnostic test that detects an immunologic response specific to an infectious agent in an individual’s serum. It looks for potential traces of pathogens in a person’s blood sample to determine whether or not that person has been exposed to the virus. It helps determine if a person has developed an immune response to the virus and can safely go back to normal life. PCR, on the other hand, is a molecular test that amplifies a specific fragment of DNA in order to increase the target DNA to detectable levels. It looks directly for the genetic material of a virus in a nasal or throat swab, instead of blood.

Procedure 

– Serology test is a simple procedure which requires loading a blood sample to be tested into an antibody test device. It looks for antibodies to viruses in the bloodstream. In the device, the antibodies bind to the antigen while the other antibodies do not bind or weakly bind to antigens because they are not trained to attack this specific virus. The device then washes off the weakly bound antigens and looks for remaining antibodies that are specific to a viral infection. If the device detects them, then it determines that the antibodies are present in the bloodstream.

PCR basically makes millions to billions of copies of a particular segment of DNA. It is composed of three steps – the first step is ‘denaturation’, which involves separating the two strands of a DNA sample apart; the second step is ‘annealing’, which specifies the region of DNA that will be copied; and the final step is ‘extension’, which copies the DNA.

Serology Test vs. PCR: Comparison Chart

Summary of Serology Test vs. PCR

Serology test is a sensitive analytical test that harnesses the unique properties of antibodies. It is a blood-based test that can detect if an individual has antibodies to a specific pathogen. At the heart of it is the binding reaction between the antibody and the antigen. It looks for antibodies to viruses in the bloodstream to determine if a person has been exposed to the virus. PCR is also a powerful procedure in molecular biology that looks directly for the genetic material of a virus in a nasal or throat swab in order to determine if the patient has an active infection.

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