Although the rate is reflected differently, the spread remains at high levels
FOR IMMEDIATE RELEASE:
February 2, 2021
COLUMBIA, SC —The South Carolina Department of Health and Environmental Control (DHEC) today announced a change in the way the positive percentage is calculated for COVID-19 cases. The change will allow South Carolina’s positive percent calculations to be more easily compared to those used by federal entities, including the Center for Disease Control and Prevention (CDC).
Starting today, DHEC is now reporting a positive percentage using the test-by-test method. The positive percentage is now calculated by dividing all positive COVID-19 tests by the total number of COVID-19 tests (positive and negative) and then multiplying the result by 100 to obtain a percentage.
With the change, the public will notice a big drop in the number that represents the positive percentage. This does not mean that the level of dissemination in the community has decreased. The positive percentage will appear to be lower just because it is calculated differently.
DHEC will not only use this new method in the future, but will also go back and recalculate the positive percentage of all the time that COVID-19 was tracked in South Carolina. Anyone who wants to see what the old data looked like can visit this link: https://scdhec.gov/sites/default/files/media/document/COVID19-Archived-Percent-Positive.pdf.
State epidemiologist Dr. Linda Bell said it is important to note that when changing methods, you cannot compare information from the old method (people about people) with the new method (tests on tests). “It is important for people to understand that, although the positive percentage appears as a lower number in the new way of calculating the rate, COVID-19 continues to spread at high levels in our state. This lower number is based solely on the change in the way we calculate the rate, ”said Dr. Bell.
“It is important that Southern Carolinians continue to take measures that we know to protect us all from this deadly disease: wear a mask consistently and correctly, stay two meters away from others, wash your hands frequently and avoid crowds. And when your time comes, get vaccinated, ”added Dr. Bell.
New calculation allows greater data comparison
With many federal agencies and state health departments using the test-on-test method, this change by DHEC will allow comparisons with percent positivity calculations provided by CDC, the White House Coronavirus Task Force, Medicare and Medicaid Service Centers (CMS) , other academic institutions and many states. In December, the CMS began to require health facilities to use test over test; DHEC began to prepare for the change at that time.
Understanding how Precent positivity is calculated
Previously, DHEC calculated the positive percentage using the people on tests method. This required dividing the number of people with positive results by the number of people who had taken the tests in general, which included positive and negative results.
DHEC decided to use this method at the beginning of the pandemic because the focus was on identifying new people with a positive test. This becomes more difficult to do when a large part of the population has been tested. With the continued recommendation that Southern Carolinians be tested frequently, switching people to testing also becomes a more effective method for monitoring active cases.
“The positivity rate helps public health officials determine the level at which COVID-19 is spreading in the community and whether sufficient testing is being carried out,” said Dr. Bell. “The fee provides us with a snapshot of how much COVID-19 is circulating in the community in a given period of time.”
What does the percentage of positivity tell us about the spread of the community?
The percentage of positivity will be high if the number of positive tests is high or if the total number of tests is low. A higher percentage of positive results suggest greater spread and that there are likely to be more people with COVID-19 in the community who have not been tested.
The percentage of positivity does not reflect a complete picture of COVID-19 in South Carolina. Although it provides us with some information about the spread of the disease, other factors are also at work, including access to tests and how quickly the results arrive from the laboratory. No single measure can provide a complete picture of the spread of COVID-19 in our state and counties.
For information on positive COVID-19 percent rates in South Carolina, visit the testing tab on the county level panel.