During the PCR test the sample taken from the patients’ mucosa of the pharynx or nose is processed. During the test the system detects the RNS of the virus in the processed sample.
Its advantage that there is no need to wait for the growth of the pathogen tested, the system is able to identify the DNS/RNS of the pathogen in the patient’s body; therefore, the diagnosis can made well before the appearance of the symptoms as well as the isolation and treatment.
The infection can also be detected if there is no immune response or when the test does not provide false positive result in case of previous infections (by then the DNS/RNS vanished from the body).
During the COVID-19 ELISA diagnostics antibodies (immunoglobulins, Ig) against SARS-CoV-2 are detected from human serum, blood plasma. The base of the test is the interaction detected among the antigens immobilized in the well of an ELISA plastic plate and the specific antibodies. Its advantage is its fast feasibility (less than 3 hours from the preparation of samples to the evaluation of results), accuracy, sample demand of low volume (few ml blood samples).
Scientific background: The first immune response to virus infection is that Immunoglobulins A (IgA) antibodies appear in the blood; this is shortly followed by IgM. After the body fought off the virus the quantity of these two antibodies suddenly falls down while the amount of a third Immunoglobulin, IgG, commences to increase. In the period after the infection the IgG level in the blood stays at a nearly equal level for a longer time.
The ELISA-based diagnostics enables the monitoring of IgA/IgM and the IgG antibodies. The previous one can be a useful supplement to the PCR diagnostics, especially, when the level of the virus starts to decrease or it becomes low and when the patient’s PCR test is negative despite the obvious symptoms of the virus infection. The IgG-based ELISA is able to detect those who have undergone the infection without symptoms even weeks before the test.