Testing! Testing! Understanding What's Good and What's Not for Testing COVID-19
“Test! Test! Test!” says the World Health Organization. South Korea tested nearly 200,000 people. Why can’t everyone do the same? Why is the U.S. Center for Disease Control and Prevention (CDC) having such a hard time with their “kits,” and why did Sweden stop testing people with mild diseases? Why are we not testing more people? The answer is “it’s complicated.”
There are more tests on the way. There are some unapproved tests that have shown up on social media promising results in “just a few minutes.” Before you jump for joy and give up your hard-earned money, please make sure you aren’t getting victimized.
1| RT-PCR Yes. Antibodies (IgM/IgG) No.
The proper test for COVID-19 and the virus that causes it (SARS-CoV-2) is known as an RT-PCR. This stands for reverse transcription polymerase chain reaction. Because SARS-CoV-2 uses RNA as its genetic material, this needs to be “reverse transcribed” into DNA before it is processed, hence the “RT.” Polymerase chain reaction is like a molecular photocopying machine that can make copies of a target DNA (in this case SARS-CoV-2) if it is present in a sample. It is so sensitive that it can detect one virus in a sample. However, RT-PCRs are technically difficult to do. A PCR machine costs several million pesos. It is dangerous to handle patient samples if you do not have the right laboratory safety equipment, otherwise all the lab people will just get infected.
The test is also easy to mess up, like what happened with the CDC test kits. So only a few labs are able to do it, but more are coming online soon. The proper specimen for an RT-PCR is a swab from the nose, throat and/or phlegm. The running time is about 3 to 6 hours and results should be back in about 24 to 48 hours. The tests done by the Research Institute of Tropical Medicine (RITM) and the UP National Institutes of Health (UP-NIH) are both RT-PCR tests.
Antibody tests usually use blood from a needlestick or a syringe extraction. These tests are for two kinds of antibodies: IgM, which is an earlier antibody produced when someone is infected with the disease, and IgG, which is produced later. IgM can be detected about five to ten days from infection, and IgG takes about 21 days. The problem with COVID-19 is that symptoms begin in about five days following infection, and so a significant number of people with early disease will still test negative on an IgM test. Almost all will be negative on IgG resulting in a false negative (there is disease, but the test is negative) test. IgM is also notoriously sticky, and so some diseases like the common cold may produce a cross-reaction leading to a false positive (there is no disease, but the test is positive) result.
So if someone offers you a COVID-19 test that looks like a pregnancy test that uses blood from your finger, just say NO. These tests are not approved by the Food and Drug Administration (FDA) and can give you either a false sense of security if it is negative or give you a positive result even if you are not sick.
2| To kit or not to kit.
There is some confusion on what a test “kit” is. RT-PCRs need different ingredients to run—enzymes, primers, positive and negative controls. These reagents can be purchased separately in bulk, or more conveniently in a “kit.” Think about making a cake. You can buy flour, baking powder, sugar, and other ingredients separately, or you can buy a readymade “cake mix” that has all the ingredients in sufficient quantities to make one cake. A PCR “kit” is the same way, it has the right ingredients in the right amount to do one test or a batch of tests. You can also buy those reagents in bulk, but as long as you use the same protocol, then whether you use a kit or an “in-house assay” it should still be valid.
The UP-NIH kit is based on this principle. Dr. Raul Destura, the developer, used the best features of different protocols and developed this homegrown RT-PCR kit. It is in the process of validation and will immensely increase our capacity to test COVID-19 once it is validated in the coming days.
However, if it is an antibody (IgM/IgG) test kit, then don’t use it (see #1).
3| Test, test, test?
This would be an ideal strategy if anyone other than South Korea had that capacity. Japan and Singapore have been ramping up, but even they do not test everybody. You also need lots of laboratories capable of doing the test safely and accurately. The cost to set up such a lab can run up to P10 million to P20 million, and it needs to be staffed with properly trained medical technologists and molecular biologists. Each test costs the government P5,000 to P8,000. While the UP-NIH kit will cost less at about P1,500, consumables for extraction and prepping will still amount to another P2,000. It doesn’t mean we don’t test, but we need to be judicious in testing. There are also subnational and private laboratories that are coming online. Hopefully they can pick up the slack as we increase the need for testing.
The Philippines has initiated drastic measures earlier than most of our neighbors to combat the spread of COVID-19. The reason is that we have learned from the experiences of China, Italy and Iran. By the time the usual thresholds for declaring widespread transmission were met in those countries, it was already too late to contain the spread.
This coronavirus is unlike anything the world has ever seen. Even the most advanced nations like the U.S. and U.K. are struggling. Our only advantage is that we started early. Let’s not squander the opportunity. Please cooperate and understand that out best chance is by social distancing and preventing further transmission. Testing will be done when appropriate.
In the meantime, stay home and stay safe.