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University of Utah Health announced Wednesday that students will go door to door to sign up thousands of Utahns for testing to see if they have ever had the coronavirus, a study that officials say will help guide state leaders in making decisions about reopening the economy.

It’s one of two major hospital chains in Utah that have announced the start of blood tests to check whether Utahns have developed antibodies for COVID-19. Intermountain Healthcare similarly announced Tuesday that its doctors will begin offering the blood tests to help add to the state’s database of where the disease is spreading.

U. students will spend the next several months knocking on doors in Salt Lake, Utah, Davis and Summit counties asking for entire households to have their blood drawn at a mobile clinic nearby and answer some questions.

The antibody tests can tell if a patient ever contracted the coronavirus, whether that person had symptoms of COVID-19 or not. This differs from the familiar nasal-swab test, which tests whether a person has COVID-19 at the moment the test is taken.

Steven Alder, who is the director of field operations for the U.'s “Utah HERO” (Health & Economic Recovery Outreach) project, said the data gathered in the randomized testing will give new insights into how many people have current or past COVID-19 infections, and which communities may have higher rates of the virus.

Alder estimated the U. will initially conduct 10,000 tests in the four urban counties.

Taylor Randall, dean of the U.'s business school, said Wednesday that the testing data will be used to guide decision-making when it comes to business restrictions and people going back to work.

“We’re navigating a careful balance between protecting public health and protecting the economy,” he said. “Anytime you’re walking a fine line like that you’ve got to have information that’s accurate, that allows you to make proper judgment. This is data that is sorely lacking.”

Dr. Eddie Stenehjem, an infectious disease physician at Intermountain, advised reporters in a videoconference Tuesday not to read too much into any particular test.

“All we can say with a person who has had a positive antibody is you most likely have been infected previously with SARS-CoV 2, the virus that causes COVID-19,” Stenehjem said. “We can’t say that you are now immune to this infection. The science of that will take awhile for us to determine.”

Both Intermountain and U. Health will have their blood tests processed by ARUP Laboratories. U. Health is now running about 200 to 250 tests a day through ARUP. Stenehjem would not specify how many tests Intermountain will conduct.

Intermountain isn’t doing a randomized testing. Instead, Stenehjem said Intermountain’s doctors will be instructed to pick patients by one of these three criteria:

• Outpatients who have had signs or symptoms of COVID-19 for more than 14 days, and had a negative nasal test.

• People who were unprotected during high-risk exposures to people with COVID-19; this would primarily be caregivers.

• People who have had a COVID-19-like illness since Dec. 1 that went undiagnosed.