Understanding Covid-19 : Testing
Now that we have managed to cover how to prevent the spread of Covid -19 and have understood how the virus spreads, we move to the third topic of the understanding Covid -19 blog.
What happens when you come in contact with someone who is Covid -19 positive?
We already know that if you come in close contact (< 6 feet) of someone who is Covid -19 positive, you run the risk of coming in contact with the droplets they secrete. They can land either directly on you body or over surfaces that you are likely to touch, eg. railings, door knobs, door bells, pens etc.
Once the virus has reached your hands, when you touch your face, the virus slowly finds its way to your nose and mouth, where it grows.
Once the virus has successfully found a host, it starts replicating and moves to the lungs where it causes symptoms. This infected host, does not show symptoms through the course of the infection in as many as 80% of the cases. But that does not mean that they cannot infect others. After the virus has replicated enough to create a high viral load in the host’s body, it starts a process known as ‘shedding’.
Shedding means that the patient’s saliva or sputum contains the virus and the patient is now infective. From what we understand about the Covid-19 infection till now, this period could last anywhere between 10-20 days and patients with serious symptoms have a higher likelihood of infecting others than those with mild symptoms, as would be expected. But does that mean that asymptomatic individuals do not spread the disease? Unfortunately, that is not true.
In Singapore, they found that in 6.4% of the infected, the infection had occurred from patients who were not exhibiting any symptoms at all. 6.4% looks like a small number, but what it means is that out of the over 10,000,000 infected all over the world, at least 60,000 patients were infected by people who did not appear to have the disease
(This is approximately the same as the entire population of France that is infected till the 4th of April!)
This is where the need for self-declaration, isolation and contact tracing arises. If you have come in contact with any individual showing symptoms of Covid-19
(fever, dry cough, difficulty in breathing);
● Isolate yourself without waiting to see if the person you came in contact with, is Covid-19 positive or not.
● Encourage the person you came in contact with, to isolate themselves and report to the health authorities. (If they do not seem keen to do so, please report them yourself.)
● Keep track of the test results of the person you came in contact with. If they test positive, you will have to inform the authorities that you are a contact too.
● Intimate the authorities if you start developing symptoms too. (Numbers given at the end of the document)
● If their test results come out negative, you should still continue the isolation till uoi become asymptomatic, and get tested again if your condition worsens.
When will the doctors test me for Covid-19?
If the doctor suspects that you have Covid-19, then you will be tested. India has modified its testing strategies depending on the curve where we were epidemiologically, as explained in the table below.
The current criteria for testing include (Version 4 , dated 09/04/2020) :
All symptomatic individuals who have undertaken international travel in the last 14 days
All symptomatic contacts of laboratory confirmed cases
All symptomatic health care workers
All patients with Severe Acute Respiratory Illness (Fever AND cough and/or shortness of breath)
Asymptomatic direct and high risk contacts of a confirmed case should be tested once between day 5 and day 14 of coming in his/her contact
In hotspots / cluster (as per MoHFW) and in large migration gatherings / evacuees centres:
All symptomatic ILI ( fever, cough, sore throat, runny nose)
Within 7 days of illness - rT PCR
After 7 days of illness - antibody testing (if negative , confirmed with rT - PCR)
Timeline for change in policies for testing and covid
February 15th
• 3 cases
• Strategy - Test travellers from Wuhan with symptoms.
• Sentinel community surveillance - Randomly test people with Severe Respiratory illnesses in the country to see if they have Covid-19 ( From February 15th to March 15th over 51 sites)
• One testing lab (4058 samples processed till March 6, 31 cases positive)
March 17th
• 143 cases
• Home quarantine for all international travellers, ban on even Indian passport holders to enter countries from Covid hotspots
• Testing for - all symptomatic travellers, contacts of positive patients, healthcare workers with severe acute respiratory illness
• By now, from 1 government lab, the capacity had been increased to 106 labs from government sector. 52 Private labs also allowed with caveat that they charge the same amount for testing.
• Government facilities to give two tests free
March 20th
• 249 cases
• All international flights banned.
• Testing for - all symptomatic individuals with international travel in past 14 days, symptomatic contacts of Covid-19 positive patients, symptomatic healthcare providers, hospitalized patients with severe acute respiratory illness ( fever and cough ± difficulty in breathing), asymptomatic high risk and direct contacts of confirmed cases ( between day 5 and 14)
April 5th
• 4289 cases
• Rapid antibody tresting introduced to identify patients in clusters where Covid-19 outbreak is seen
• 139 Government labs now working 7 days a week to test samples
• 56 private labs now approved
• Covid testing and treatment free in private labs and hospitals under Ayushman Bharat
• Anyone with flu-like symptoms, advised home quarantine.
• Home made or cloth masks recommended for general population use.
If you have been exposed to someone who is later found to be Covid-19 positive, when should you get tested?
Like we spoke before, the virus starts replicating once it is inside the host. Once the host starts shedding, the virus can be isolated and hence tested. Once you take into account, the life cycle of the virus, the best time to get tested, is between 5-14 days after contact if you are asymptomatic. If you do have symptoms, you will be tested immediately.
Where are the samples taken from?
Depending on the nature of the test, the sample will be drawn.
RT-PCR test, ID NAT – Swab from nose into the back of your throat, from the mouth into the back of your throat or sample from inside the lungs for the critically ill
Rapid antibody – Blood
How long will it take for you to get your result?
The RT-PCR test is performed in two parts. One provisional and a second confirmatory. Each test takes around 6-8 hours. So, you might receive your results one day after you have sent the samples.
The newly launched Mylab kit (Designed and made in India!) is a new addition to our weaponry. It not only reduces the time required for diagnosis to 2.5 hours, it also costs less than a third of the conventional RT-PCR test. It is now being made available all over the country, and should ease the pressure on diagnostics in addition to faster results.
What about the test by Abbott that has launched? It gives results in 5 minutes.
Something that needs to be borne in mind regarding this test is that it is not FDA approved. Keeping in mind the global outbreak and urgent need for newer and faster diagnostic modalities, the FDA has granted temporary authorization. The test will then be independently be validated at a later stage to test how accurate and sensitive it is in comparison to the conventional tests.
Unlike the rapid antibody test, this test identifies the virus itself and so, it promises to be more accurate. The Abbott test is a point-of- care test, meaning, it will deliver results out of a toaster sized box that is portable and convenient. The test uses a swab similar to the RT-PCR test. It works by identifying a small portion of the genetic make-up of the virus, replicating it to make the virus more detectable and then giving results. Abbott claims that positive results will be obtained in as little as 5 minutes and negative results will be available in 14 minutes. This is obviously great and will be a game changer in diagnostics, but they are not being marketed yet in the USA or India. Abbott has increased its production lines and hopefully these tests will be available soon.
What is the rapid antibody test that has been launched? Is it any good?
Antibodies are the body’s defence mechanism for any illness. So, they are generated only after an individual has been infected. Now these antibodies are of two types, IgM and IgG. IgM is seen in the body during the course of the infection and last up to 28 days. IgG on the other hand, starts increasing by 21 days and can be seen for months to years later. IgG is what forms the body’s infection memory.
By identifying antibodies in the blood, and confirming which kind they are, it is thus possible to get an idea if the person is infected or was recently infected and that too rapidly and by means of a simple prick!
How will rapid antibody test help prevent the spread of Covid-19?
The problem with the antibody test, is that it only comes positive after the body starts attacking the virus. Which means that in someone whose immune system takes longer to attack, the test results could get delayed. In those with weakened immunities, it could take even longer. What it translates into, is that the positive result depends on how well your body fights the infection. Since the conventional tests rely on identifying the virus itself, they remain more accurate.
If you look at the recent developments in the country, you will notice a change in the administrative policy. Initially, if someone tested positive, they only isolated that individual and traced contacts. Now, as the numbers increase, they have started what is termed as ‘cluster containment’. If a person in a particular locality tests positive, they lock the whole place down for 14days, no one in or out. Though it sounds Draconian, it ensures that the virus does not have the opportunity to leave the locality. Once everyone is locked down, they trace contacts, find the symptomatic people and test them. We know that in 14 days, everyone who could possibly have been infected, will show symptoms and be detected. In a locked cluster, we assume that everyone has met everyone else, so any cough and fever, may be Covid-19. Antibody tests play a big role here. You quickly check everyone who has the slightest complaint and those who are close contacts. If the test is positive, you know that they either have the infection of have had it. If they test negative, and are contacts, they will do a RT-PCR test too, to confirm.
But again remember, since this is an antibody response that is being measured, a negative test will have to be repeated in 10 days to ensure that they are indeed negative.
When is someone said to be Covid-19 positive?
The diagnosis is confirmed only after two RT-PCR tests are done. They can either be done on the same say, where swabs are taken from two different places, or they might take a swab from the same place on two different days, to ensure accurate results.
What if I test negative?
If you test negative, and there is a strong suspicion that you might have Covid-19, you will be tested again even if you are asymptomatic. If there is no such suspicion, you will just be asked to continue your quarantine at home to prevent others from getting your flu-like illness.
Can I test negative and later test positive?
This is one of the regrettable drawbacks of the current testing modalities. It is possible for you to test negative on the first occasion and then test positive, even on RT-PCR. If the viral load is so low that you have not started shedding yet, then you are likely to test negative initially. Given this backdrop, patients in whom there is a strong suspicion of Covid-19, due to a close contact with known patients, tests are repeated once again between 5 and 14 days to confirm. Isolation is advised till then.
How do the doctors know that someone has recovered from Covid-19?
When the patient no longer has any symptoms of the infection, they test negative for two swabs taken 24 hours apart, the patient is said to be cured.
A question that people keep asking, is why don’t we just test the entire population? We will know where we stand.
Well that’s true. We’ll know where we stand, but only where we stand today. Whether you use RT-PCR techniques or antibody testing, it is possible that someone who is infected, will continue to remain unidentified unless, everyone is tested every five days! A staggering 1.3 billion tests, every five days would have to be done to ensure that no one is missed out. Even with the cheaper Mylab kits, the costs would be over Rs. 18,20,00,00,00,000 just on the tests alone, every time we test!!!! This ginormous amount of money is definitely better spent on providing tests to those who need them, better healthcare facilities to those who are ill and providing Personal Protective equipment to the doctors and nurses.
Despite this let us assume it were possible to test everyone and we did, what are we likely to get? For those who believe we definitely have higher number of cases and we are under reporting, even if we were to assume that the total mortalities in one of the top three nations (USA, Spain, Italy) is the true number for India that would mean for the ~10,000 deaths we should have reported we have a total 2,00,000 cases in the country. What would we have advised the rest of the 1,90,000? We would have isolated as them, since there is no cure! And that is precisely what we are doing presently for everyone, with our nationwide lockdown in place anyhow! Recent news has amply shown that we cannot predict which individual in the society may have been to a location with positive cases or travelled along with such individuals either. Hence, home isolation is the best answer anyway at present.
If we stay home, we reduce the cluster spread. The sooner we all do this, the lesser the spread and the earlier we can go back to our routine lives where the sun, the sands, the breeze, the moon and the stars await us… Not to forget the restaurants and the shopping and most importantly going out becomes less like a stealth mission and more of a pleasure! And in the end... Stay home Stay safe Stay healthy.
Guest Blog Credit
Dr Gauri Gangakhedkar Anaesthesiologist, Researcher KEM Hospital Mumbai
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