“Those are the people that we want to test,” said Dr. Keith Starke, Mercy’s chief quality officer, at a news conference at the testing site Friday afternoon. “We start testing everyone, the system becomes overwhelmed.”

And screening too early, before symptoms appear, can result in a false negative, he added.

State coronavirus testing has gotten faster. Mercy has been able to get results within 24 hours, Starke said. He added that the timeline can be longer through other labs.

The temporary testing site is at 15740 South Outer Forty Road in Chesterfield. It is outside of a Mercy building that offers telehealth services and does not typically see in-person patients.

Testing at the drive-thru site means patients will spend less time in crowded hospitals. It may also relieve some of the pressure felt by hospitals during the outbreak.

“It keeps it out of the emergency department,” said Fran Hixson, director of clinical quality and infection prevention for Mercy. “It really, really helps them focus on other medical needs.”

People must call Mercy’s COVID-19 Clinical Support Line at 314-251-0500 before arriving.