Molecular, serological and antigenic tests, knowing the differences to see clearly

Who I am
Marie-Ange Demory
Author and references

Source: Shutterstock

The latest developments in the health emergency tell a worrying picture with respect to the spread of the coronavirus in all regions of the country. The combination of Covid-19 and school had already opened scenarios impacting the lives of families with children who have returned to schools of all kinds and levels and new procedures to be followed for the safe return of students to the classroom: at this time it becomes important to distinguish the differences between molecular, serological and antigenic tests to understand how to move and optimize the steps. If the DPCM of October 19 had already changed the school experience of high school children (with a period of schools closed in Campania in their entirety), today the scenario appears even more jagged: with the DPCM of October 25, 2022 which increases the limitations professional and personal, having a clear understanding of the possibilities of tracing the virus is very vital. With a look at the status of the integration of the so-called rapid salivary antigenic tests: the arrival of rapid swabs at school (procedure still being validated and disseminated nationwide) could modify and streamline the current test situation.

In this article

  • Differences between molecular, serological and antigenic tests, an overview
  • Distinguish the tests used for tracking Covid-19
Read also: Covid-19 and open windows in the classroom. Let's take stock

Differences Between Molecular, Serological, and Antigenic Tests: An Overview

Molecular test (pharyngeal or nasopharyngeal)

Since the outbreak of the Covid emergency in Del Paese in February 2022, the molecular test or the pharyngeal or nasopharyngeal swab was the only effective way to counteract its spread, identifying it safely in positive patients. The biological material collected from the investigation through exploration of the buccal and nasal cavities ensures a result that is the most reliable possible compared to the tracking methods subsequently integrated.

Explaining the difference between a swab and a serological test to children is almost as important as explaining the swab to children and preparing to run it in such a way as to check for the presence or not of the virus.

Serological tests

I serological tests they have been integrated to streamline the tracking procedures and have been a useful tool in view of the reopening of the Regions in June 2022 and the return to school of teachers and school staff. The investigation, carried out on a blood sample, is not as reliable as that of the molecular test but is useful for verifying the presence of antibodies in the blood fluid. In the event of a positive serological test, the Ministry of Health recommends swabbing. 

I test antigenici

I antigenic tests are the novelty of autumn 2022 and are destined to radically change the approach to tracing: this method of analysis (carried out by means of a swab or saliva) indicates the presence of viral proteins (antigens) capable of binding to antibodies and returns the response with a unique sign, Yes / No. They are tests that can also be easily analyzed by the pharmacist, fast and efficient, from which a result is obtained in 15 minutes. They could be the turning point for tracking in school or airport and professional environments.

It flies, i salivary antigen tests: also these antigenic but declined only on the analysis of a salivary sample, which may present (even if in a smaller quantity than the molecular buffer) the presence of the virus. Although efficient tests already exist on the market, they have not yet been integrated into the health system and among fast tracking methods in a massive way, but some schools from 29 September 2022 have included them in their tracking practices, and so have airports.

Read also: Covid-19 and children: why their immune response is more effective

Distinguish the tests used for tracking Covid-19

How the molecular buffer works

Thanks to a flexible stick (cotto-fioc) a rhino-pharyngeal or pharyngeal survey is carried out for a sampling of mucus and saliva. The purpose of the swab is to check for the presence of viral genetic material (virus RNA). Currently it is the most effective test in the world, but it also has its limitations, due to the slowness necessary for the validation of the results that can only be carried out in the laboratory. 

How serological tests work

In this case, a blood sample is taken (or a drop of blood from the fingertip) to obtain three different types of results. A positive serological can demonstrate the presence of IgM antibodies and indicate that the infection is recent; the presence of negative IgM antibodies e positive IgG antibodies, which indicate an infection that occurred in the past but has already ended. A negative serological test instead it can indicate three statuses of the patient: a non-infection of the patient with SARS-CoV-2 virus or an infection too recent for the development of antibodies. The latter is also the most controversial and indicates a person infected but with too low levels of antibodies to be recognized by the test. Serological tests are considered excellent tests for screening and epidemiological analysis of Covid-19 in one or more sectors.

Also read: Covid-19 in children: it is less lethal and causes milder symptoms

How rapid antigen tests work

In common with the swab, the antigen test can be performed through a nasopharyngeal swab but the method of anal and research changes compared to the molecular one. If in the first case we look for the RNA of the virus, in the case of rapid antigen tests we go to look for the virus antigens, viral proteins which are able to bind to antibodies and be recognized as potentially dangerous for the immune system. The speed with which the analysis of this type of antigen test is carried out is the real added value: the results are verifiable in 15 minutes and there is no need for them to be carried out in the laboratory, as reported by an ISS document dedicated to differences between the various methods of tracking current positivity.

How salivary tests work

Salivary tests have already been introduced in some schools since 30 September 2022, as reported on the website of the Ministry of Health. They are considered very effective for early tracking in all those cases where speed becomes essential for the optimization of procedures (for example airports or precisely in schools). They are always part of the family of antigenic tests, only in this case the salivary sampling is not carried out through a nasopharyngeal swab but by mouth, taking a sample of saliva. As always reported by the Ministry of Health, the results of these tests are less reliable than the others but remain a valid support for "speeding up the diagnosis of suspected cases of COVID-19. And this is because" the frequency of febrile episodes in the school population in the period in fact, autumn and winter will presumably be very high and it will be necessary to often resort to the practice of the swab to quickly exclude the possibility that it is COVID-19 and to quickly identify cases, isolate them and trace their contacts, facilitating the decision to apply or fewer quarantine measures in a short time and with a considerable saving of resources, avoiding an excessive overload of the reference laboratories. "The SalivaDirect produced by the Yale School of Public Health was approved in August 2022 by the FDA (US Food and Drugs Administration) and is currently one of the most reliable kits on the market.

Sources for this article: Ministry of Health School, green light for rapid antigen tests as a prevention tool; US Food and Drug Administration Coronavirus (COVID-19) Update: FDA Issues Emergency Use Authorization to Yale School of Public Health for SalivaDirect, Which Uses a New Method of Saliva Sample Processing; ISS Epicenter ISS ISS Covid-19 Report No. 11/2022. 

  • coronavirus
  • virus
add a comment of Molecular, serological and antigenic tests, knowing the differences to see clearly
Comment sent successfully! We will review it in the next few hours.