State adding antigen test results to online COVID-19 data

The Minnesota Department of Health (MDH) announced today that it will begin posting on its website COVID-19 cases detected using new antigen testing equipment approved by the FDA under an emergency use authorization.

In posting these cases, MDH is following the guidance of the Council of State and Territorial Epidemiologists (CSTE) – the independent professional body that determines case definitions for the country. CSTE guidance subsequently affirmed by the U.S. Centers for Disease Control and Prevention (CDC) indicated that someone who has a positive antigen test for COVID-19 should be considered a probable case. The guidance comes amid reports that the antigen tests have lower accuracy than the “gold-standard” polymerase chain reaction (PCR) test process. However, the cases will receive the same level of case investigation and follow-up as cases confirmed using the PCR test.

Antigen testing is a technology used to determine whether someone is actively infected with COVID-19, just like the lab-based PCR tests that to this point have been the primary testing systems used in the COVID-19 response. One advantage of antigen tests is that they generate results more quickly than the traditional PCR method. Another advantage is that they can be used by providers who do not have a full laboratory set up to do testing.

Even with these advantages, there are some drawbacks. Antigen tests are not considered to be as reliable as PCR tests. The U.S. Department of Health and Human Services has provided large numbers of antigen tests to long-term care facilities to conduct the frequent testing required by the federal officials, but it is not clear whether the antigen testing devices provided to states by the federal government are sufficiently accurate when used to test people without symptoms.

“Federal officials have embraced antigen tests and are aggressively encouraging states and institutions across the country to use them,” Minnesota Commissioner of Health Jan Malcolm said. “We believe it’s a good idea to add this equipment to our toolkit as long as we keep the information in proper context. Our goal is to work with long-term care facilities and others who’ve received these devices to make sure they are used in the most accurate and effective manner, and to learn more about this testing method as we go.”

MDH Infectious Disease Director Kris Ehresmann welcomed the new testing tool while also emphasizing that testing is part of a comprehensive COVID-19 response that includes the tried-and-true prevention measures.

“It is very important to understand that testing – even rapid testing – is not a substitute for other preventative actions,” Ehresmann said. “Tests can have false positives or negatives, and people can develop illness after they are tested. Even as we continue to expand our testing capacity in Minnesota, people still need to continue to socially distance, wear masks, avoid crowds, wash their hands and stay home if sick.”

Antigen tests were first approved for use by the FDA in May, and CSTE updated the case definition for COVID-19 to include antigen testing and consider them a probable case in August. MDH received laboratory reporting of the first antigen test results in June.

The data on antigen testing shown on the MDH website will be added to the information the department currently reports. Total tests, total cases, total cases by county and test positivity will be broken out by PCR/confirmed and antigen/probable. Demographic data on cases will continue to be combined and include antigen test results. The initial posting will include antigen testing data going back to Sept. 1, 2020.

MDH cautions that with the new testing devices going out to many facilities not as accustomed to reporting disease data to public health officials, there may be some initial challenges with timely and thorough reporting to the department. To help reduce the chance of delays and inaccuracies, the department is developing a robust set of guidance for those using antigen testing equipment.

-MDH-