Coronavirus test: How many options do we have, when and what are they used for?
The new coronavirus SARS CoV-2 (COVID-19) first appeared in the Chinese city of Wuhan and poses a new threat with its true impact still unknown. Characterized by high transmissibility, any consequences on the health of the world population will have a very large impact in the future.
The main types of diagnostic tests are the molecular analysis method (real time RT-PCR) for the detection of virus RNA, the rapid detection of virus antigen by immune chromatography and the various tests for the detection of antibodies to the virus.
Each type of test has advantages and disadvantages. The use of each type is chosen according to the purpose of the control, the occasion, and even based on the means available.
Molecular method of PCR analysis
It is based on the detection of viral particles in clinical respiratory specimens (nasopharyngeal or oral pharyngeal mucosal smear), with methodology specificity and sensitivity approaching 100%.The test is performed by simultaneously detecting at least two of the Orf1ab (RdRP), E and N genes of the SARS CoV-2 virus (COVID-19), which is recommended by international organizations.The results are usually available after 24 hours, while there is a quick variation with the results being available in a few hours.
· When is it recommended? This method is the basic reference test that confirms that the virus actually exists in the body. It is recommended for everyone, when the active disease must be confirmed, regardless of whether it is symptomatic or not. The method of detecting antibodies against the virusThe body develops three types of antibodies against the virus, IgA, IgM and IgG.
The test is performed with blood sampling, but there are more practical, faster tests performed with a drop of blood, with less sensitivity or otherwise more likely to show false negative results in the early stages of the infection.IgG antibodies are the adapted and highly specific viral immune response and are very important for the development of long-term immunity. IgM antibodies are produced by the immune system fairly quickly and provide first-line defense. IgA antibodies indicate a very recent infection with the virus.
· When is it recommended? The antibody test method is recommended only for epidemiological studies and not for the primary diagnosis of infection, as well as as a screening in patients who have become ill and have already tested negative for Molecular Testing (PCR). In some cases, detecting these antibodies can help identify patients who have been asymptomatic.
The “pooling” method The “pooling” method, which means the simultaneous detection of the virus from at least five samples together, after mixing them, is used mainly for the purpose of epidemiological research. When such a sample is positive, a second analysis of the samples follows at an individual level, in order to separate the positives. Its main disadvantage is that a pooling process involving samples with low viral load often leads to false negative results.
• When is it recommended? The above fact is the reason why, although it was developed as a method that allows great savings in the number of tests when there is a shortage, but also as a much cheaper method, it is recommended only for epidemiological research.At Aegean Medical Service, all examinations for the coronavirus, the processing and analysis of the samples, are conducted in the privately owned certified laboratories of the Group.
The COVID-19 molecular test currently uses the technique of unit / individual analysis. At the same time, the Group closely monitors the developments in medical and technological level worldwide, in order to integrate new detection methods, always focusing on the accuracy of the results and guided by safety.