EVANSTON, Ill. — NorthShore University HealthSystem just became the first local hospital network to perform its own in-house coronavirus testing for patients who are symptomatic and ill.

Already about 400 patients a day are being tested at Evanston Hospital, Chicago’s Swedish Hospital and others in the NorthShore network. The health system is gearing up to do at least 500 tests daily.

“The faster we know the faster we can make sure they are in the appropriate isolation and that our staff are protected. Because it is imperative that right after protecting patients, we protect our healthcare team,” said Sean O’Grady, NorthShore University HealthSystem.

O’Grady said many facilities have been waiting two to five days for test results. NorthShore expects to have results in about four hours.

NorthShore started developing the test in late January after the RNA sequence for COVID-19 was shared globally. The effort is expected to ease the burden on state labs, but testing at NorthShore is reserved for when it is warranted.

“We are only testing patients with symptoms. What I would ask is that people please not tax the healthcare system if you are not having symptoms. We know that everybody is very nervous — we appreciate the anxiety — but we need to reserve our testing for those who are ill,” said O’Grady.

An estimated 10% of people who have been tested by NorthShore tested positive for COVID-19.

In-house testing has given same-day results to doctors who are able to make better decisions on isolating patients, or sending them home.