A preliminary study reported earlier this week cast doubt on the efficacy of the Abbott device. A group of researchers from New York University said the machine missed between a third to nearly half of positive cases caught on a competing device, although the study has not yet been peer-reviewed.

Abbott has rejected those findings and sought to soothe investors on Thursday evening.

“It’s unclear if the samples were tested correctly in this study,” the company told The Washington Post in a statement. “This rate has been previously shared with the FDA. In communications with the users of the test, it is performing as expected.”