WASHINGTON, Dec. 17 (Xinhua) — COVID-19 testing kits developed by the U.S. Centers for Disease Control and Prevention (CDC) in the pandemic’s early weeks contained a design flaw that caused false positives, a recent internal review has found.

The CDC previously disclosed that the polymerase chain reaction tests developed in January 2020 were contaminated but had not acknowledged the basic design flaw, according to The New York Times, citing the analysis published earlier this week on PLOS One.

The faulty test kits, the document showed, were distributed to laboratories in early February 2020, with many reporting that the tests produced inconclusive results.

Experts say the faulty tests hurt national efforts to detect and track COVID-19 cases across the United States.

“It delayed the availability of more widespread testing,” Benjamin Pinsky, director of clinical virology at Palo Alto, California-based Stanford Health Care, told the Times. “I think it’s important that they got to the bottom of what went wrong.”

PLOS One is a peer-reviewed open access scientific journal published by the Public Library of Science (PLOS) since 2006.