Coronavirus: US death rate likely to fall as new rules allow for wider testing
- Rule change means independent laboratories will be able to use their own tests, making them available to less severe cases
- US fatality rate stands at about 4.5 per cent, compared with 3.9 per cent in mainland China
Testing for Sars-CoV-2, the clinical name for the virus, has expanded since the US government heeded a call from the American Society for Microbiology (ASM) for the US Food and Drug Administration (FDA) to lift “emergency use authorisation” restrictions that prevented clinical microbiology labs from using their own independently developed tests.
That change took effect on February 29, more than five weeks after the first US case was confirmed. Other public health protocols that had kept the denominator of confirmed cases in the US low – such as guidance that discouraged testing of anyone who had not travelled abroad to areas most affected by Covid-19 – have also been cleared.
With too few FDA-approved tests and screening criteria limited to individuals with particular travel histories or with more severe symptoms, US public health officials were testing a subset of cases more likely to progress towards death.
“When you test very widely, then your denominator becomes very large, so the case fatality rate will go down,” said Benhur Lee, Ward-Coleman chair in microbiology at the Icahn School of Medicine at Mount Sinai in New York.
The newly relaxed regulations will allow several diagnostics companies to start offering their own tests at medical practices and clinics in the US. For example, Quest Diagnostics said it would start making its tests available this week.