With successes in countries like South Korea, Taiwan, and Germany, testing and contact tracing have proven to be the crucial weapons for the survivability of nations under economic duress during this war against an invisible enemy.
Some countries have seen crucial failure in testing roll-outs. In February, the United States rejected using the WHO approved and validated test kits early in the process. It sent out its CDC (Centers For Disease Control) test kits that were faulty and produced inconclusive results. Samples had to be sent to its central laboratory in Atlanta. Not only were there a shortage of test kits available, flawed kits and travel time obliterated America’s ample lead time against the virus.
With federal response and coordination in shambles, states were forced to search for their own resources for testing. Losing pivotal time, the FDA eventually loosened its restrictions in March.
With little assistance from the federal government, states had to individually scramble for supplies and test kits from other countries and providers.
On April 16th, an NBC News article called out at least two cities and two states that are currently using unapproved COVID-19 antibody tests including Denver and Los Angeles and urgent care centers in Maryland and North Carolina. The concern was that these test kits were not approved by China’s Center for Medical Device Evaluation (a branch of China’s FDA-type agency) or by the U.S. FDA.
Two U.S. companies Premier Biotech of Minneapolis and Aytu Bioscience of Colorado have been distributing tests after the FDA relaxed its guidelines in March. Tests made by two Chinese manufacturers Hangzhou Biotest Biotech Co. (provides to Premier Biotech) and Zhejiang Orient Gene Biotech (supplies Aytu Bioscience) are not approved on the list and are being sold in the US. The article suggested that the Aytu kits had “considerable number of false positives”. Nonetheless, this may be anecdotal because the LADPH partnered up with University of Southern California and an independent study published in Infection Ecology & Epidemiology supported its reliability.
The fact remains that none of the current testing methods have undergone the rigorous examination for FDA approval.
Why aren’t any these tests FDA approved?
At the moment, the U.S. does not have any “FDA-approved” diagnostic methodologies. The severity of inadequate testing in the Unites States forced the agency to loosen its restrictions. As of this article, the FDA website currently states “There are no FDA-approved diagnostics for COVID-19.” Test kits are authorized under FDA’s Emergency Use Authorization (EUA).
In the war against COVID-19, testing is the number one weapon. But like all arsenals, one interminable fact remains: NOT ALL TEST KITS ARE MADE EQUAL.
The main methodologies for the determination COVID-19 infection are as follows:
1) Real Time Reverse Transcriptase Polymerase Chain Reaction (RT-PCR)
What is RT PCR?
Once a nasopharyngreal swab is inserted, it’s twisted enough times in hopes of picking up a piece of the RNA VIRUS that is COVID-19. Since RNA is complementary to DNA, a DNA complementary is created and added to an enzyme called reverse transcriptase with complementary primers in the mix.
A single copy of DNA is multiplied through processes called denaturation, annealing, and extension. Each cycle to double a strand of DNA lasts ten minutes and the process is repeated to produce roughly one trillion copies.
Getting a good sample is CRUCIAL. If no virus gets on the swab, PCR will not be able to detect it.
How long does this test take?
Varies from hours to days.
One step requires less time than two step PCR method but each process is time consuming.
Is one RT-PCR Test more accurate than another?
This test measures the amount of specific RNA using fluorescence. RT-PCR products are put through gel electrophoresis. Two step RT-PCR is more accurate than one step RT-PCR with a longer turn around time.
How reliable is this test?
The test is a real-time reverse transcription–polymerase chain reaction (rRT-PCR) assay that can be used to diagnose the virus in respiratory and serum samples from clinical specimens.
The original CDC rRT-PCR test was recalled due to ineffective reagents. The CDC has since developed an updated protocol that excludes the need for third component that was causing the problem.
RT-PCR is currently considered the “gold standard” for tests.
On April 13, 2020, the FDA granted EUA for a saliva-based COVID-19 test, which can be used to test patients’ self-collected saliva rather than swabs collected by healthcare personnel, potentially limiting exposure and increasing the capacity for testing.
Self-collected swabs new increase false negatives due to improper collection.
2) Antibody testing
The FDA also approved a two immunoglobulins: M (IgM) and G (IgG) antibody test for COVID-19. This test uses blood drawn samples from plasma or whole blood.
What is IgM and IgG?
Immunoglobulins are antibodies produced by the white blood cells in our lymph nodes that, when stimulated, create antibodies against viruses or bacteria.
The problem with a novel virus is that the human body has never encountered it; thus, no previous antibodies have been formed against this invader. The average person is expectedly without any initial defenses, thus, no immunoglobulins specific to COVID-19. It can take a few days for the human body to react and create IgM’s and even longer for IgG’s.
The science behind the test is what is typically seen in most home pregnancy tests called lateral flow immunochromatographic assay. While pregnancy tests detect hormones, blood/serum are introduced along a surface of a pad with reactive molecules to detect IgM and IgG.
How long does this test take?
Like a pregnancy test, this test only takes minutes.
Is one antibody test more accurate than another?
Tests have not been proven by large, peer reviewed studies but results of smaller studies have been promising.
Premier biotech partnered up with the University of Southern California to assess its sensitivity. Two different investigations found the tests’ positive results for COVID-19 were correct 99.5 and 100 percent of the time.
A small independent study published in Infection Ecology & Epidemiology showed Aytu’s Rapid Test Kits had a sensitivity of 69% and 93.1% for both IgM and IgG, respectively. The assay showed an overall specificity of 100% for IgM and IgG, respectively.
Cellex qSARS-CoV-2 IgG/IgM Rapid Test, the first serological test authorized by the FDA, notes a Positive Percent Agreement and Negative Percent Agreement of 93.75% (95% CI: 88.06-97.26%) and 96.40% (95% CI: 92.26-97.78%), respectively in its package insert.
- How reliable is this test?
Timing is a big issue for this test. The study also showed that IgM had a lower sensitivity as IgM is present for initial acute response. Antibody tests will be negative if used very early in the illness.
Rapid IgG and IgM may not be effective screening tool for very recent exposure. The Hoffman study tested patients between 9 and 21 days after the onset of symptoms.
Asymptomatic candidates who are newly exposed should never be recommended for this test on its own. Most importantly, this depends on an individual immunogenic response to an antigen that the body has never before seen. It may take days after infection for the body to react and create the necessary antibodies that would show a positive test.
The speed and cost effectiveness of the test, however, are perfect for basic screening of possible asymptomatic secret spreaders, and ascertaining immunity to the virus. Viral immunity can last months to an entire lifetime.
The test may also be used to verify immunity against the virus though the degree of which and how long the immunity lasts still need further studies.
3) Isothermal Nucleic Amplification
This test is a polymerase chain reaction test developed by Abott. It uses the same methodology as a polymerase chain reaction except it does not require the thermal cycles and produces results within minutes.
This Abbott ID NOW COVID-19 test machine is also highly portable, which is perfect for immediate results and point of care testing.
How long does this test take?
As little as five minutes for positive results and 13 minutes for negative results
No independent studies were found, but the FDA has authorized its use under EUA.
4) Viral Cultures
- Australian scientists have successfully grown the virus in cultures.
- Viral cultures not recommended for reasons of biosafety.
5) Medical Imaging
Chest CT scans are helpful for diagnosis of COVID 19 but is not recommended for routine screening. When screening tests weren’t available early on, some doctors had to rely Chest CT’s for suspected cases.
Chinese study Fang et al noted a high sensitivity of 98% but poor specificity. Bai et al study noted that, COVID-19 compared with other viral pneumonia, showed a peripheral distribution.
Bai et al noted the following results on chest CT features of COVID-19 patients:
Peripheral distribution (80%), ground-glass opacity (91%), fine reticular opacity (56%) vascular thickening (59%)
It's important to ask about the testing methods available in your hospital/testing center.
Speak with your healthcare provider as to the types of methodologies available and what they mean for you.
Until a vaccine or cure is available, prevention and testing is the only proven arsenal against this invisible enemy.
1. Sandler, Rachel. “How The CDC Botched Its Initial Coronavirus Response With Faulty Tests.” Forbes, Forbes Magazine, 9 Mar. 2020, www.forbes.com/sites/rachelsandler/2020/03/02/how-the-cdc-botched-its-initial-coronavirus-response-with-faulty-tests/.
2. Morgenson, Gretchen. “Unapproved Chinese Coronavirus Antibody Tests Being Used in at Least 2 States.” NBCNews.com, NBCUniversal News Group, 17 Apr. 2020, www.nbcnews.com/health/health-news/unapproved-chinese-coronavirus-antibody-tests-being-used-least-2-states-n1185131.
3. Hoffman, Tove, et al. “Evaluation of a COVID-19 IgM and IgG Rapid Test; an Efficient Tool for Assessment of Past Exposure to SARS-CoV-2.” Infection Ecology & Epidemiology, vol. 10, no. 1, 14 Apr. 2020, p. 1754538., doi:10.1080/20008686.2020.1754538.
4. “Coronavirus Disease 2019 (COVID-19) Workup: Approach Considerations, Laboratory Studies, CT Scanning.” Coronavirus Disease 2019 (COVID-19) Workup: Approach Considerations, Laboratory Studies, CT Scanning, 16 Apr. 2020, emedicine.medscape.com/article/2500114-workup.
5. “Cellex QSARS-CoV-2 IgG/IgM Rapid Test.” U.S. Food and Drug Administration, Cellex, Inc, www.fda.gov/media/136625/download.
6. Fang, Yicheng, et al. “Sensitivity of Chest CT for COVID-19: Comparison to RT-PCR.” Radiology, 2020, p. 200432., doi:10.1148/radiol.2020200432.
7. Bai, Harrison X., et al. “Performance of Radiologists in Differentiating COVID-19 from Viral Pneumonia on Chest CT.” Radiology, 2020, p. 200823., doi:10.1148/radiol.2020200823.
[V1]100% for both IgM and IgG?
Special Thank You’s:
Dr. Vince Cabahug, MD
Dr. Kylan Pathmanathan, MD
Dr. Mark Mabalatan, MD