On Feb. 6, a scientist in a small infectious disease lab on the Centers for Disease Control and Prevention campus in Atlanta was putting a coronavirus test kit through its final paces. The lab designed and built the diagnostic test in record time, and the little vials that contained necessary reagents to identify the virus were boxed up and ready to go. But NPR has learned the results of that final quality control test suggested something troubling — it said the kit could fail 33% of the time.

Under normal circumstances, that kind of result would stop a test in its tracks, half a dozen public and private lab officials told NPR. But an internal CDC review obtained by NPR confirms that lab officials decided to release the kit anyway. The revelation comes from a CDC internal review, known as a "root-cause analysis," which the agency conducted to understand why an early coronavirus test didn't work properly and wound up costing scientists precious weeks in the early days of a pandemic.