Coronavirus tests are still extremely difficult to get in the U.S.

The big picture: A lot of labs are now making tests, and testing capacity is steadily increasing.

• But some areas have the ability to get results in hours, while others must wait days, as the Wall Street Journal reports. That's because some patients are receiving care closer to the testing facility than others.
• States, counties and providers all have different criteria for who should be tested, and some of these criteria are still very limited — meaning that some patients with signs of the coronavirus aren't getting tested.
• Some providers don't have enough protective gear, and so aren't testing patients in order to avoid infecting health care workers.

What's more, shortages of testing supplies may threaten our testing capacity in the near future.

• As Politico reported Monday, there may be shortages in RNA-extraction kits that are a necessary component of the tests.

• The New York Times reported yesterday that labs are also facing potential shortages of key chemical ingredients and having trouble obtaining other testing materials.

The bottom line: "What's most important now is there is still a significant shortage of reagents, and laboratories are really scrambling to get access to the reagents," Karen Carroll, director of the Division of Medical Microbiology at John Hopkins, told me. "That's the crisis we're all facing right now."

Go deeper: The two uncertainties of the coronavirus