Covid tests

Covid disease is currently spreading everywhere. 

Coronas are currently being tested in public and private labs. 

When to check? 

Which investigation is more convincing? 

Which test costs more? 

Which test takes how long? 

What is HRCT and its score? 

What is the difference between rapid antigen test and RT-PCR? 

All these things we will see in this Corona article.

There are two main types of corona probes

1) Viral Test

2) Antibody Test

Antibody Test is not used to diagnose corona.

Viral Tests are mainly used to diagnose corona. In addition, HRCT is used to diagnose the increased incidence of the disease in the body, as well as to understand the severity of pneumonia and lung function.

There are three main types of viral tests.

1. Rapid Antigen test

2. RT - PCR

3. True Nat Test

Time to check

1) Rapid Antigen test - half an hour

2) RT - PCR-- 24 to 48 hours

3) True Nat Test - half an hour

4) HRCT - half to one hour

Which check should be done when

The Government of Maharashtra has given the following guidelines for this.

Antigen Test

a.) In patients who need immediate treatment

RT - PCR

a.) Patients with a negative Antigen Test but with symptoms.

b.) People in contact with a corona positive patient.

c.) People coming from abroad.

True Nat Test

a.) Brought Dead person

b.) Mothers who have come for childbirth

c.) Emergency Operation Patients

(If True Nat test is not available, Antigen test should be done.)

The Maharashtra government has not allowed HRCT to diagnose Kovid. This test is not considered valid by the government for covid diagnosis.

Let us now see the details of all the investigations.

Rapid Antigen Test

1) It examines the antigen protein in the surface spike of the virus.

2) For this swab is taken from the nose and throat.

3) We can understand the report of this test in half an hour.

4) This test is cheaper and faster than RT-PCR test.

5) Well Trainer is not required for this test.

6) Defects in inspection

a. In flu-like illness with corona-like symptoms, the sensitivity of the test is only 34 to 80 percent.

By the same token, this test can be negative in half or more covid positive patients.

b. Many asymptomatic (asymptomatic) patients do not get the right amount of virus from the nose and throat, so this test can be negative.

This is because the antigen is not amplified in this test.

7) Then why this test is done ??

a.) This test is highly sensitive when the viral load is high. This makes it easier to isolate the infected patient.

b.) This test is healthier and faster than RT-PCR.

c.) To reduce the stress on RT-PCR tests when it is not possible to perform RT-PCR tests on all patients.

d.) To isolate positive patients accordingly by screening as many people as possible during community spread and to prevent the spread of the disease accordingly.

e.) Patients who have symptoms despite having a negative antigen test are then screened for RT-PCR.

f.) Antigen machine is cheaper than Treu Nat machine and it is possible to do a large number of tests on this machine simultaneously.

RT - PCR

Reverse Transcriptase Polymerase Chain Reaction

1) It involves the production of thousands of times the DNA from a small amount of RNA by certain chemicals which are available in the right amount for testing (even if there is a small amount of virus in the swab).

2) This is the most reliable and accurate test for covid diagnosis.

3) But this test is very time consuming. It may take 24 to 48 hours for the report to arrive.

4) For this swab is taken through nose and throat. Or spit may be taken to check.

5) This test requires a properly trained person.

Which is not so necessary for the other two checks.

6) Corona virus mainly grows in the throat in the first week after which it starts growing in the lungs. This means that a throat swab is positive for a period of one week after infection. Then Throat swab is more likely to be False Negative. This requires examination of the tracheal swab or phlegm in the second week of infection.

Many videos have been seen that when you ask for an RT-PCR report, ask for the CT value (Cyclic Threshold) in it. If it is more than 24, then the viral load is less in that person, that is, the infection is less to that person through that person, and if the CT value is less than 24, then that person is more viral load, that is, these people spread the infection to others.

Although this is true, it is often the case that the symptoms are mild or moderate in spite of the viral load. Such as young children who rarely have severe symptoms but are highly susceptible to infections.

Older people, on the other hand, have less severe viral load but more severe symptoms.

This is in fact a paradox.

And the reason for this is that the complications that occur in covid are not just caused by viruses entering the body. So it is mainly due to how much and how the immune system responds to the virus and this is due to the inflammatory changes that take place in our body. Immune system reactions and the resulting inflammatory changes vary from patient to patient. And as a result, some people do not show any symptoms, while others may develop a lot of complications.

The CT value mainly indicates the viral load. This is not how dangerous Kovid can be. Therefore, ICMR does not allow CT value in RT-PCR report

TrueNAT test

1) This machine is made by Malbio Diagnostic company in Goa.

2) This machine was used to test for TB in the past. ICMR recently approved the machine to test COVID 19.

3) This machine is small in size and can be carried anywhere in a briefcase.

4) This machine runs on battery. Once the battery is charged, it can run for up to 10 hours.

5) In this machine only one test can be done at a time. If the machine has 4 slots, a maximum of 4 tests can be done at a time. There can be a maximum of 45 tests in an 8 hour shift.

6) This machine is mainly used in remote areas where the number of large labs is less and it is also difficult to take swabs and send them to large labs for RT-PCR.

7) In this test also the genome of the virus is amplified like RT-PCR. Therefore, even though the amount of toxins in the swab is low, the test report is accurate.

8) This test mainly detects the E gene of corona virus and the enzyme RdRp present in the RNA of the virus.

9) This test is much faster than RT-PCR (half to an hour) and also costs less for this test. (Rs. 1200 to 1300) Also this test is easy to do and does not require any specially trained person.

10) However, due to the high cost of this machine (6.5 to 12 lakhs) and low supply, this machine is not yet available everywhere.

Antibody Test

1) When an antigen (any living organism like bacteria, virus, etc.) enters the body, the components that are produced by the body to fight them are called antibodies.

2) Antibody test mainly gives information about previous diseases.

3) It takes about 1 to 2 weeks for the body to produce antibodies after infection. Therefore, this test is of no use for the diagnosis of covid.

4) Not all people will develop symptoms in Kovid. This test is mainly used to find out how many people have contracted the disease and to determine the mortality rate from the disease.

HRCT

1) This test is a CT scan of the chest.

2) This test is not considered by the government for diagnosing covid.

3) However, 4 to 5 days after the onset of symptoms, if the incidence of the disease increases in the body, this test is used for diagnosis as well as to understand the severity of pneumonia and lung function.

4) Compared to RT-PCR, it is reported immediately and also shows the severity of pneumonia.

5) Like RT-PCR, its report is more reliable and accurate. It can also accurately diagnose whether it can improve the patient's body or worsen the patient's condition.

6) HRCT is not so sensitive in the first 4 days after the onset of symptoms, so HRCT report is likely to return to normal in 50% of covid positive patients. But then HRCT is Highly Sensitive.

7) The following symptoms may appear in the report of HRCT

a.) Early (within 7 days after onset of covid symptoms) - Ground Glass Opacity (GGO)

b.) If pneumonia develops after 7 days ---

1. GGO growth

2. Crazy paving pattern

3. Consolidation

4. Fibrosis

8) HRCT Score

a.) Score is given in HRCT to understand the extent to which pneumonia has increased in the lungs.

b.) This score is between 0 and 25. A score of 0 means that pneumonia is not widespread in the lungs, while a score of 25 means that pneumonia is widespread in the lungs.

c.) When the score is out of 25

1) Low pneumonia - having a score less than 12.

2) Moderate pneumonia - having a score of 12 to 18.

3) Acute pneumonia - having a score above 18.

d.) HRCT Score is multiplied by 4 to find out the percentage of lungs affected. But that is not always the case.

e.) In most of the reports HRCT score is given out of 40, then both the above rules do not apply.

9) C Reactive Protein along with HRCT to find out if the patient's pneumonia can increase or decrease.

 Serum ferritin and lymphocytes should also be tested.

10) X-rays do not show the initial GGO-like symptoms of covid, so X-rays are not as useful for diagnosing covid.