We asked an expert at HudsonAlpha Institute for Biotechnology to help us understand the science behind the increasingly many tests being done across the country for COVID-19. As you would expect, money is one of the non-science factors that also comes up. The following are answers from Neil Lamb, PhD, vice president for Educational Outreach at HudsonAlpha.
Accurate testing is critical to identifying and tracking the spread of COVID-19, the disease caused by SARS-CoV-2.
The type of testing currently being used is molecular — it looks for the presence of the viral RNA in the sample (typically a swab from the nose, throat or lungs of an individual suspected of being infected). The sample is sent to a testing lab, where technicians extract the genetic information and search for the RNA sequence specific to the SARS-CoV-2 virus. Different technologies and approaches may be used, but the entire process generally takes 4-8 hours to obtain results. Because coronaviruses use RNA rather than DNA as their genetic code, the laboratory will often first make a DNA-based copy of any viral RNA present in the patient sample. The test looks at the genetic material present in the sample, searching specifically for the genetic information that is unique to COVID-19, that is not found in other types of coronaviruses.
In the early stages of the global pandemic, the testing process was slow to roll out in the United States. COVID-19 testing was initially only allowed at the Centers for Disease Control and Prevention headquarters in Atlanta, but local and state public health laboratories were later given permission to offer testing. Many private testing labs also have created their own COVID-19 screens, working under an FDA policy that allows rapid development and deployment of these tests.
The benefit of molecular testing is that it is very sensitive — it is the ‘gold standard’ right now. However, it takes time to do the test, as well as sample processing and reporting. Overall turnaround time varies from a few hours to a few days. The test is relatively expensive (often $100 or more). Importantly, the molecular test only detects ACTIVE virus infection. If you had symptoms, but have since recovered, it is likely a molecular test will give you a negative result.
The other type of test is a serological test, sometimes called an “antibody test.” These are slowly coming to the market. Serological tests look for evidence that an individual’s immune system has responded to fight the COVID-19 infection by producing antibodies to the virus. They are typically very rapid tests, taking only 15-30 minutes. Unlike a molecular test, a serological test can identify people who have recovered from COVID-19 days or weeks ago. This can help researchers and medical professionals track the spread of the virus. These tests are believed to also detect individuals who experienced very mild symptoms, or even were symptom free, although some preliminary research suggests this may not always be the case. Serological tests will not identify a patient in the early stages of infection and they can be less sensitive than a molecular test, producing negative tests when the individual is actually positive. Nonetheless, they may prove useful in identifying people who have developed an immunity to the virus and thus are safer to return to the workplace, especially in critical areas.
Currently all testing must be done by professionals in a laboratory or medical setting. Further out in development could be options for self-testing, through a swab of the nose or throat, that individuals could send to a lab, or even an at home test, that could deliver results at home, directly to the patients. Both of these options are being explored by researchers as ways to both expedite testing and make it more widely available.