What you need to know about the diagnosis of the latest coronavirus?
What you need to know about the diagnosis of the latest coronavirus - SARS-CoV-2?
Today, two main methods are used to diagnose COVID-19 (a coronavirus disease caused by the SARS-CoV-2 strain, first detected in December 2019 in Wuhan).
Rapid tests (immunological method: test strips to detect IgG + IgM antibodies in the patient's blood). No additional equipment is required, the result is known in 10-15 minutes, but can be considered reliable only when tested in the acute phase of the disease (7-8 days after the onset of symptoms), earlier, due to low antibody titers, may give a false negative result.
Therefore, they are usually used for primary testing - confirmation should be by molecular genetic diagnostics - namely PCR (polymerase chain reaction).
PCR diagnostics (test systems for detecting virus RNA even in the early asymptomatic stage of infection by the natural mechanism of multiple multiplication of genetic material using Taq polymerase and hybridized labels attached to each copy, and, accordingly, the detection of such a large amount of material by specialized equipment.)
For a successful PCR study, it is necessary to qualitatively isolate RNA from the patient's biomaterial - washes and swabs from the oropharynx and nasopharynx, bronchoalveolar lavage, lung biopsy material and more. Isolation is done manually or automatically using commercial reagent kits (it is important that they are compatible with the kits to detect the virus itself).
An important point is the presence of a suitable thermal cycler (amplifier, PCR analyzer), which will read the results of the study using the APPROPRIATE test system. The difficulty lies in the presence in the device of detection channels of a specific hybridized label, which is used in the test system, the information is always specified by the manufacturer.
So, the main points to pay attention to when purchasing a PCR test system:
- RNA isolation system (a set of reagents must provide the appropriate level of extraction and purity of RNA);
- test system should pay attention to the number of stages of the study - whether there is a set for reverse transcription (ST), or ST and PCR occurs in one or two steps.
Most foreign manufacturers have implemented the One-Step system - CT and PCR take place in the device, not separately. It is also important to know how many genetic markers determine the presence of the virus (the virus itself is a small RNA sequence capable of frequent mutations, so the developer's task is to find and select primers for areas that are NOT prone to mutations).
General recommendations of the WHO and CDC, FDA include at least three genetic targets:
- two to detect the actual SARS-CoV-2 (most often - N gene, RdRP gene from the open reading frame ORF1b);
- one for the detection of SARS (E-gene).
You should also pay attention to test systems that use additional internal control and material capture control, such as RNAase P). Compatibility of the test system with the amplifier. The following models of thermal cyclists are the most available and popular in Ukraine, so the representative needs to clarify the adaptation of the test system to your device:
- "DT" DT-96, DT Prime, DT Lite (DNA Technology).
- Rotor-Gene (Corbett Research).
- «IQ5», «CFX96» (BioRad).
At the same time, we want you to follow the rules of quarantine, avoid contact with people with symptoms of SARS and avoid crowds. If you feel unwell, consult your family doctor.
Take care of yourself and your loved ones!