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Molecular and rapid antigen test kits: the role of in vitro diagnostic medical devices in the pandemic of Covid-19

In vitro diagnostic medical devices play a very important role today in the context of the Covid-19 pandemic, in detail for the detection of SARS-COV-2 virus and since for tracing activities. The diagnostic medical devices on topic are divided into two types: molecular tests and rapid antigen tests.

These IVDs are regulaed by Directive 98/79 /EEC and almost always fall within the “other type of IVD” category, for which the manufacturer follows a conformity assessment procedure according to Annex III.

Among the requirements that the legal manufacturer must meet in order to place on the market these devices, there is the preparation of a self-declaration of conformity and the develop of a technical file that collect evidences that argue the compliance with the essential requirements applicable to the product.

Using these tests is today a chance for obtaining the Covid-19 Green Pass. In detail, it is necessary a negative result from a molecular test swab carried out in the last 72 hours or from a rapid antigen test during the previous 48 hours.

From May 26, 2022 2017/746 EU Regulation will be applied and will repeal Directive 98/79/EEC, therefore molecular and antigen test kits that detect SARS-COV-2 will fall into risk class D. In this case obtaining a product certificate from a Notified Body will be a prerequisite for legal manufacturers to place on the market these kind of IVDs.

How do rapid antigen tests work?

Molecular test kits detect the presence of the virus through its nucleic acid (RNA) using the real-time RT-PCR (Reverse Transcription-Polymerase Chain Reaction) technique, which, in a summary, can be described as the amplification of genes virals that are more present due to the infection. The analysis is carried out in highly specialized laboratories.

Rapid antigen test kits, on the other hand, identify the pathogen through its proteins (antigens). These IVDs present as substrates specific viral binding antigens of SARS-CoV-2. The antigen-antibody reaction can be visible to the naked eye or read by simple equipment.

These tests are especially useful in cases where a clinician needs, in a short time, information that allow to develop a diagnosis. The rapid antigen tests, in fact, allow to reach the result faster (typically 15-30 minutes are sufficient) compared to the molecular test kits.

Moreover test can also be carried out directly at the point of care level without the need to be carried out in a laboratory, thus becoming a near patient testing device. Furthermore, some manufacturers have designed and certified rapid antigen tests that can be directly used by lay users, making them fall into the category of self-testing. In this case, in order to be placed on the market, they must obtain a certificate from a Notified Body.

Furthermore, rapid antigen tests are also valid tools for screening investigations. However the sensitivity and specificity parameters of such tests are generally lower than those of the molecular test kits; therefore it may be necessary also the application of a molecular test as further control.

For both types of tests the main method of sample extraction is nasopharyngeal swab. For rapid antigen tests, IVDs are also available whose sample collection mode is based on salivary or nasal swab only. The latter case is available especially for rapid self-testing antigen tests.

Among the services that Di Renzo Regulatory Affairs provides to stakeholders there is registration of IVDs inside the database of the Ministry of Health and the complementary evaluation of documents such as labels / instructions for use / declaration of conformity.

Di Renzo also supports legal manufacturers in the implementation of the activities necessary to obtain the CE marking both as regards the quality management system and the preparation of technical file, working together with Notified Bodies and accredited laboratories.

Written by: Antonio Ciriello

Foto di Tho-Ge da Pixabay