Iowa poised to change its method of calculating virus positivity rates

    A worker checks a clipboard at a Test Iowa site in Waukee on June 17, 2020. (Photo by Kathie Obradovich/Iowa Capital Dispatch)

    The Iowa Department of Public Health is changing the way it calculates and reports the state’s coronavirus positivity rate.

    The net effect of that change will be a lower positivity rate as the state factors in a greater number of negative tests tied to individuals who, because of their jobs or other factors, take the test repeatedly. In recent weeks, Iowa’s positivity rate has hovered around 26%, meaning more than one of every four tests that is counted by the state results in a “positive” finding.

    Beginning this week, IDPH officials will calculate the state’s positivity rate by dividing the number of positive tests over a two-week period with the total number of tests, both negative and positive, administered during that same time period. That is the same method used by the U.S. Centers for Disease Control and Prevention to calculate positivity rates, according to IDPH, and should result in more accurate state-to-state comparisons.

    As things stand now, the 14-day positivity rate in Iowa is computed using the number of individuals who tested for the virus rather than the larger, total number of tests given.

    IDPH Interim Director Kelly Garcia said that at one time, during the pandemic, approximately 125,000 Iowans had been tested, but 1.3 million total tests had been  conducted. “And now, just four months later,” she said, “we’ve nearly doubled the number of individuals tested and tripled our total tests.”

    Clark Kauffman
    Deputy Editor Clark Kauffman has worked during the past 30 years as both an investigative reporter and editorial writer at two of Iowa’s largest newspapers, the Des Moines Register and the Quad-City Times. He has won numerous state and national awards for reporting and editorial writing. His 2004 series on prosecutorial misconduct in Iowa was named a finalist for the Pulitzer Prize for Investigative Reporting. From October 2018 through November 2019, Kauffman was an assistant ombudsman for the Iowa Office of Ombudsman, an agency that investigates citizens’ complaints of wrongdoing within state and local government agencies.