Testing for Coronavirus
VIRUS INFECTION CYCLE
When one is infected with COVID-19, the virus grows and multiplies in your body over the course of 5-7 days. Suppose that on day 1 of the infection, you have 1 particle of the virus. On day 2 it may multiply to 100 particles. On day 3 it might reach 1,000 particles. On day 6 it might reach 100 million particles. Days 5-10 is the most infectious period. After day 8 or 9 is when one begins experiencing symptoms. The ideal time to get tested is 1-2 days before one starts showing symptoms to minimize any possible spread. Since we cannot test ourselves daily (cheap tests are not yet available), we recommend getting tested immediately as one begins to experience symptoms. Refer to the graph for a better illustration.
The novel coronavirus has proven to be deadly. At the end of August, 185,000 people have died in the US and 844,000 have died worldwide. The death toll is expected to cross over 200,000 in the US as per the CDC. Coronavirus doesn’t seem to be as deadly in children as compared to adults. However, studies have shown that children carry up to 100 times the viral load of an adult. Therefore, children can carry the virus home and spread it to grandparents and other family members. To ensure everyone’s safety, it is best to test and quarantine. There is no cure or vaccine available for the coronavirus, therefore the only way to protect ourselves and others is to minimize the spread of this virus is to identif infected persons and isolate them.
WHEN TO TEST?
Once you start to show symptoms, your body has already been infected for a few days. If cheap daily testing were possible, one could detect if they could transmit the virus very early on in the period of infection. However, since they are unavailable, we recommend getting tested immediately as you begin to experience symptoms. This way, if you are positive, you can minimize any potential spread of the virus. If you were to get tested a few days after your symptoms began, you would expose anyone you come in contact with to the virus. As previously explained, those first 5-10 days are when people are most infectious.
WHAT KIND OF TEST?
There are broadly two kinds of tests - ones which check if you have the virus now (virology) and others which check if you had the virus in the past (serology).For more information, watch this video.
Virology- diagnostic tests
o Reverse Transcription – Polymerase Chain Reaction (RT-PCR)
A sample is taken from your nose and in the PCR machine, a single strand of the COVID viral RNA is amplified to detectable levels. The single stranded RNA is then changed into double stranded DNA; this process is called reverse transcription (RT). This DNA is then multiplied so there can be a large enough quantity of viral DNA to detect if the virus is in the sample. This technique is considered to be the gold standard, therefore the test is 100% specific. This means if it is positive, it is 100% accurate. It is also 100% sensitive. This means if it is negative, it is 100% accurate. The RT PCR can detect very low amounts of RNA in a sample, up to 100 genomes copies/ mL. One concern with the RT-PCR we have seen is that, it can detect very small remnants of RNA during retest after 2 weeks of an infected patient. We cannot be sure that if the RNA is part of the live virus or if it is dead leftover RNA. The RT PCR tests take anywhere from 1 to 8 hours to run at an independent lab and results are typically available in 24-48 hours at our clinic. The sample is taken with a nasal swab (not the deep nasopharyngeal swab) and we are also testing the reliability of saliva samples. For more information, watch this video.
o Nicking Enzyme Amplification Reaction – (NEAR)
NEAR is also a molecular test and results are available in 5-15 minutes. We use Abbott ID NOW. We are one of the few clinics in the country to get the IDNOW COVID tests this early. Unlike the RT PCR, it does not do repeated heating and cooling and the test is run with one temperature (60 deg. C). It uses proteins to target pieces of the COVID virus to make more copies with a kind of genetic copier-printer template. Other proteins find the copied pieces of the virus and “nick,” or cut, the replicated viral code out of that template like a paper cutter at the end of a printer. This rapid copy print of viral sequences is what allows for a positive ID of COVID-19 in just a few minutes. Specificity and sensitivity are lower than the RT PCR and it can detect about 10,000 genome copies/ mL. If the test is positive, the results are ready in 5 minutes. If negative, results are ready in about 15 minutes. The sample is taken with a nasal swab (not the deep nasopharyngeal swab) or a throat sample. For more information, watch this video.
o Antigen test
Antigens are proteins on the surface of viruses that alert your body that there is an infection. The antigen test looks for antigens specific to COVID-19 and reveals if a person is currently infected. Once the infection has gone, the antigen disappears. We use The Sofia SARS Antigen FIA in our office. It’s a point-of-care test based on lateral flow technology. Results are available in 15 minutes. The test is 100% specific. This means if it is positive, it is 100% accurate. It is also 100% sensitive. This means if it is negative, it is 100% accurate. The RT PCR can detect very low amounts of RNA in a sample, up to 100 genomes copies/ mL. The sample is taken with a nasal swab (not the deep nasopharyngeal swab). For more information, watch this video.
There is a new antigen test (BINAX NOW) which was given emergency use authorization by the FDA. It is called the "$5” COVID test and it also takes 15 minutes. It is made by Abbott who makes the ID NOW machine that we have. It’s the same method as the Sofia 2 except it is read by the human eye and not by a machine. The federal government has bought all tests to be produced (150 million) until the year end. It is unclear who will get these tests or when. We used to use BINAX NOW for flu and RSV. Since we were one of the few clinics to get the IDNOW COVID tests this early, hopefully we can get this new test soon. We will keep our patients posted on this new development. For more information, watch this video.
Serology- Antibody tests
An antibody test reveals if a person has already been exposed to an infection, by detecting antibodies in their blood or serum. Antibodies are like solders created by the body to fight specific viruses. There are 2 kinds of antibodies IgM (short term fighters) and IgG (long term fighters). Antibody tests are not usually used to diagnose current infection as it takes the body some time to produce antibodies. Data suggests that in the case of COVID 19, it takes about 2 weeks to produce the antibody IgM followed by the IgG antibody peaking at three weeks.
Antibody tests cannot be used to determine if someone has COVID 19. We do not do antibody tests at our clinic. Antibody tests can help us to track the spread of disease, giving a more accurate representation of the COVID-19 pandemic. The FDA had removed the authorization for Antibody Tests due to “significant clinical performance problems were identified that cannot be or have not been addressed by the commercial manufacturer”. Additionally, there are a large number of fake tests in the market from overseas. It is unceratin how long the protection will last even if IgG status is known. There is no “immunity passport” according to WHO. For more information, watch this video.
The tests (PCR and rapid) that we use at Bay Colony Pediatrics are all authorized for emergency use (EUA) by the FDA until the end of the pandemic. We do not buy any tests from the internet or foreign sources.
TEST RESULT REPORTING
If one is positive for the COVID 19, we are required by law to report to the county of their residence. The county officials might contact you directly for contact tracing. The Sofia 2 directly send the results to CDC wirelessly.
For additional information about testing at Bay Colony Pediatrics click here.