Understanding the numbers: Changes in state’s reporting of COVID-19 testing data

Federal CDC-privided Coronavirus test kit. (Kent County Health)

By WKTV Staff

ken@wktv.org

Both Michigan and Kent County report COVID-19 numbers routinely, but a big question these days is what specifically does those numbers mean — people who are sick, people who had the virus and did not get sick, people who never contracted the virus for whatever reason?

Kent County, for example, reported 3,385 cases as of May 23 (with 68 deaths), while statewide numbers had 54,881 “confirmed cases” as of May 25.

The Michigan Department of Health and Human Services (MDHHS) announced last week that it had changed the way it reports data on COVID-19 testing to make those numbers a little clearer.

“The change makes the data more accurate and relevant as the state continues to expand diagnostic testing to help slow and contain the spread of COVID-19,” the Man 23 MDHHS statement read. “The update to the website separates out the results of two different types of tests – serology and diagnostic. Michigan – along with some other states – has not separated data for diagnostic and serology tests.”

 

Data on serology testing – also known as antibody testing – is separated from the other testing numbers. Currently, serology testing can be used to help determine whether someone has ever had COVID-19, while traditional viral diagnostic tests determine if someone has active disease.

“Accuracy and transparency are paramount as we continue to respond to this pandemic,” Dr. Joneigh Khaldun, chief medical executive and chief deputy for health, said in supplied material. “We continue to expand and improve data reporting to make sure the public understands where their community stands with the COVID-19 outbreak.”

Digging into the numbers  

MDHHS emphasizes that the change in reporting does not affect the number of lab-confirmed COVID-19 cases in Michigan. It does lower the percentage of positive tests over the last nine days — when serology testing became more common. Michigan’s overall percentage of positive tests since the beginning of the outbreak remains virtually the same — changing from 14.2 percent positive tests to 14.3 percent.

Michigan’s COVID-19 website now shows results for 512,891 total tests reported to the state – with 450,918 diagnostic test results and 61,973 serology results.

Diagnostic tests are most helpful in tracking the spread of COVID-19 since they can show the number of people who currently have the COVID-19 virus. Serology tests are still being studied regarding their utility.  They are currently most helpful in understanding how much a community may have been exposed to the disease.

“However, it is unknown if the presence of an antibody truly means someone is immune to COVID-19, and if so, for how long,” the statement continues. “Results of antibody tests should not change decisions on whether an individual should return to work, or if they should quarantine based on exposure to someone with the disease.”

 

Approximately 12 percent of Michigan’s tests overall have been serology tests; about 60 percent of those have been from the past nine days.

Testing data can be found on the Lab Testing page of Michigan’s coronavirus website.

 

Information around the COVID-19 outbreak is changing rapidly. The latest information is available at Michigan.gov/Coronavirus and CDC.gov/Coronavirus.

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