Editorial: More and Better COVID-19 Testing Needed
Key findings
- Patients who have a clinical presentation consistent with COVID-19 may warrant lower respiratory tract sampling and continued isolation despite an initial negative molecular test result
- In the public health setting, the best test is not necessarily one that determines whether a person is infected with the SARS-CoV-2 virus but rather one that quickly and accurately identifies individuals capable of transmitting the infection to others
- Antigen tests play that role—helping to limit the spread of infection—because they identify patients with infectious virus, including asymptomatic individuals, rather than simply those with viral RNA
- Rather than consider testing as a COVID-19 prevention measure, it is more accurate to think of it as a mitigation strategy along with physical distancing, mask wearing and avoidance of large indoor and outdoor gatherings
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Multiple efforts are underway to create new diagnostic tests for COVID-19 and novel testing platforms. In a recent editorial in JAMA, Katrina Armstong, MD, physician-in-chief in the Department of Medicine at Massachusetts General Hospital, and colleagues explain why these innovations are needed.
Testing Alone Is Insufficient for Clinical Care
In general, the current molecular tests, which amplify viral RNA, are more sensitive than antigen tests. Still, false-negative results can occur due to sampling problems and the timing of the test during infection. Patients who have a clinical presentation consistent with COVID-19 may warrant lower respiratory tract sampling and continued isolation despite an initial negative molecular test result. Many hospitals have developed diagnostic algorithms that include a wide range of variables.
The Role for Antigen Tests
Epidemiologic evidence has demonstrated that the pandemic is being driven by asymptomatic and pre-symptomatic transmission of the SARS-CoV-2 virus, including within households. In the public health setting, the best test is not necessarily one that determines whether a person is infected with SARS-CoV-2 but rather one that quickly and accurately identifies individuals who are capable of transmitting the virus to others.
There is limited knowledge about the clinical and microbiologic characteristics of infectivity in either asymptomatic or symptomatic patients, in part because upper respiratory samples have to be cultured in biosafety level 3 containment laboratories. However, studies of patients with symptomatic COVID-19 suggest the infectious period lasts from about two days after exposure to 12 days after symptom onset.
Antigen tests help limit the spread of infection and help prevent large outbreaks by rapidly identifying people at highest risk of transmitting disease. These tests identify patients with infectious virus, including asymptomatic individuals, rather than simply those with viral RNA. They can be easily performed by untrained personnel and give results in less than 15 minutes.
A Coordinated Strategy Is Needed
Recent highly publicized outbreaks of COVID-19, such as on university campuses and at the White House, are a stark reminder that testing alone is insufficient to prevent community transmission. Rather than consider testing as prevention, it is more accurate to think of it as a mitigation strategy. Physical distancing, mask wearing and avoidance of large indoor and outdoor gatherings must remain central to public health strategy even as tests become faster, more sensitive and more specific.
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