Tests and diagnostics for Covid-19.

Real-time molecular biology test RT-PCR is a test method to determine the presence of viruses through the detection of the genetic material of the SARS-CoV-2 virus, which is a highly accurate method. According to CDC recommendations, the real-time RT-PCR test is the "gold standard" for diagnosing Covid-19.

An antibody test (serology) is a blood test that looks for the virus indirectly through the determination of antibodies in the blood. Antibodies are special proteins (IgM, IgG) that the body produces to fight infections. Normally, after an infection, it takes a while for the body to produce detectable antibodies in the blood. Performing the test can effectively detect people who have been infected with the virus before. However, it is not very effective in detecting new infections.

Step 1: Prepare before sampling. Healthcare workers performing sampling should ensure biosafety principles for infectious diseases, including:
Wear the right protective gear and the right way.
Wear N95 respirator and helmet, goggles, face shield.
Wear 2 layers of medical gloves.
Perform disinfection and do not wear protective gear out of the sampling area.

Step 2: Take the specimen. Medical staff taking samples include:

– Take 3 – 5 ml of blood into the EDTA anticoagulation tube.

– Respiratory fluid: Use a sampling stick to perform upper and lower respiratory tract samples:

Upper respiratory tract fluid: Throat fluid, nasopharyngeal fluid, throat rinse.
Lower respiratory tract fluid: Sputum, alveolar fluid, endotracheal fluid, pleural fluid, lung tissue, bronchi, alveoli.
– Put the 2 sample strips that have been taken into the same tube of available virus transport medium.

Step 3: Preserve the sample. Once the sample is collected, the specimen should be sent to the laboratory as soon as possible.

Samples are stored at 2 – 8oC and transported to the laboratory 48 hours before sampling.
Samples are stored immediately at -70°C if transit time is expected to exceed 48 hours.
Do not store samples at -20°C or in the freezer compartment.
Whole blood samples can be stored for up to 5 days at 2-8°C.

Step 4: Pack and transport samples to the laboratory.

Tighten specimen type cap and cover with paraffin paper, cover each specimen type with blotting paper.
Place the sample in the sample carrier bag.
Cover the transport bag with absorbent paper, cotton soaked in water containing disinfectant (Cloramin B...). Then place the specimen pack in the second plastic bag and tie it tightly.
Close the specimen collection slips into the final plastic bag, tie it tightly and transfer it to a cold thermos, with the logo of biological specimens painted on the outside, and then proceed to transport.

Currently, there are two techniques for detecting antibodies:
ELISA technique helps to quantify the concentration of IgM and IgG antibodies in the blood, on average it takes 1-5 hours to get the result of antibody concentration in the blood.
The immunochromatographic technique (rapid test or rapid test): qualitative antibody, similar to the pregnancy test. This technique is simple, low cost, fast results. It only takes 15-20 minutes to have results with or without antibodies.

Faster with results in just 15-20 minutes.

With antibody detection tests such as the rapid test, the test results are preliminary and screening only. The main purpose of this test is early detection of suspected cases, medical isolation if necessary. In many cases, patients who are tested negative for 2-3 times can still have the disease. In contrast, when the sample is taken between days 5 and 6, the positive rate is higher if the person already has the disease.

- A positive test result shows that you have antibodies from infection with the virus that causes Covid-19. However, there is still the possibility that that positive test result is a PASSIVE POSITIVE. After that, it is necessary to take samples from the pharynx, pharynx, and sputum to perform a confirmatory test for Covid-19. At the same time, conduct medical isolation of the patient.
- Negative result: subject was not infected with the SARS-CoV-2 virus at the time of sample collection. However, this test has a HIGH rate of PASSION, with about half of NEGATIVE results being incorrect.

However, testers continue to monitor their health status and isolate for 14 days. The rapid test can be performed again after 5-7 days.