PCR, antigen, and antibody testing … words we stumble upon daily. But do we know what they mean?

Testing is still relevant for initial screening and diagnosis of potential infections. At the same time, COVID-19 testing is indispensable to keep monitoring the vaccine effectiveness.

Let’s analyze the substantial difference between the various types of tests for COVID-19’s identification. 

Molecular test (PCR)

Molecular tests detect the genetic material of the virus, giving the confirmation of the infection in progress. In other words, it is used to detect the presence of the virus in the body. 

PCR tests are the most attentive test to confirm whether the patients have active infections. Generally, the false test’s negative rate is around 9.3%. False-negative can happen, mostly due to the pre-analytic phase. Some of the main reasons might be attributed to improper test collection or little virus presence. 

The test specimens need to be analyzed in the lab by professionals.

Antigen test (rapid tests)

The antigen test for COVID-19 is a qualitative investigation based on the search for viral antigens expressed on the surface of SARS-CoV-2.

The methods of collecting the biological sample are entirely similar to those of molecular tests (nasopharyngeal or oralpharyngeal swabs). 

However, antigen tests differ from molecular tests as they do not require lab equipment. They can be deployed for rapid screening of potentially infected patients. The result can be obtained within 20 minutes.

Unlike the molecular swab, the antigen test does not identify specific traces of the RNA genome of the SARS-CoV-2 virus. It detects some components of the virus (Spike proteins and Nucleocapsid) indicative of exposure to the viral agent.

Serological tests (antibody testing)

Serological tests make it possible to detect the presence of antibodies against the SARS CoV-2 virus. Simply put, antibody testing detects the body’s response to the infectious agent and is used to understand if a person has already developed an immune response following the COVID-19 infection. 

Through serological tests, it is possible to identify the antibodies produced by our immune system. 

Test samples can be blood from a fingerstick or vein.

How do serological tests work?

There are two types of serological tests: qualitative and quantitative. The substantial difference lies in the methodology and method of analysis:

  • Qualitative tests are the well-known rapid tests in which a drop of capillary blood (obtained with a finger picker) is sufficient. Qualitative tests only establish whether a person has developed antibodies or not, according to a positive/negative logic.
  • Quantitative tests can measure IgM or IgG antibodies quantities. 

Quantitative testing requires a precise measuring instrument and insights are derived from a mathematical analysis.

How is the PCR test analysis performed?

The biological material taken with the swab is analyzed in the laboratory using the method known as quantitative real-time PCR. 

The first phase of the analysis consists of extracting the nucleic acids to identify viral RNA (ribonucleic acid).

Once the RNA is obtained from the biological sample, its amplification is carried out. The specific genetic markers of SARS-CoV-2 (viral RNA) are searched and quantified.

Molecular tests are the most reliable method for detecting even very low concentrations of viral RNA. 

Conclusion

In light of the previous considerations, it can be stated that:

  • The molecular RT-PCR test remains the reference test for the diagnosis of SARS-CoV2.
  • Rapid antigen tests on nasopharyngeal swabs can be helpful in specific contexts, such as rapid screening of many people.
  • Antibody tests can confirm a past infection. Through this type of testing, we can isolate and cure unaware carriers. 

Regardless of your country, we strongly suggest seeking reliable health care providers. We recently come across Wondfo Biotech. The company has over 30 years of experience in the health care industry. 

Wondfo has been in the front line for COVID-19 response, providing support with antigen, antibody, and PCR testing to 140 countries worldwide.

To know about Wondfo COVID-19 testing solutions, check out their website.