Sens. Warren, Smith press major labs over coronavirus testing delays as flu season approaches
Sens. Elizabeth Warren and Tina Smith pressed five of the nation's largest testing labs over delays in processing coronavirus tests as the flu season approaches.

Labs across the country have struggled to keep pace with the rapid rise of coronavirus cases earlier this summer, leading to long lines at testing centers and turnaround times of more than a week for some patients. Billionaire philanthropist Bill Gates said that long turnaround times render coronavirus tests a "complete waste" because it takes so long to get results that people can't self-isolate once they find out they have the virus.

"Delayed test results and the inability to conduct enough tests seriously weakens the country's efforts to combat the pandemic. Delays in results can obfuscate public health officials' view of the virus and how it is spreading, hindering their ability to respond effectively and, in turn, prolonging the pandemic," the senators wrote in five letters sent Wednesday to the nation's biggest lab companies. The letters were viewed by CNBC. "While testing numbers and turnaround times have improved in recent weeks, it is imperative we take steps now to prevent future delays and backlogs."

Public health officials such as Dr. Ashish Jha, professor of global health at Harvard University, have echoed Gates' concerns. A survey run between July 30 and Aug. 10 by CNBC in partnership with Dynata, a global data and survey firm, suggested that almost 40% of Americans at the time had to wait more than three days for their results, rendering them clinically useless, by Jha and others' definitions.

The Democratic senators expressed concern about testing challenges in states that were hit particularly hard by the virus this summer such as Florida, Texas, Arizona, and California.

"Tens of thousands flocked to testing sites in these states and across the country, and labs and local officials struggled to keep pace," they wrote. "Public health officials have even been forced to turn away patients from testing sites and re-impose testing restrictions."

Warren, D-Mass., and Smith, D-Minn., sent letters to Quest Diagnostics , LabCorp , the Mayo Clinic, BioReference Labs and ARUP Labs. In the letters, the senators asked each of the companies to tell them the current turnaround time for coronavirus testing, maximum daily capacity as well as their turnaround time and capacity during July and August. They also asked the companies to let them know if they've faced any shortages in supplies needed to process Covid-19 tests.

Quest, LabCorp, ARUP Labs and Mayo Clinic confirmed that they received the letter and are reviewing it. Representatives of BioReference Labs did not return CNBC's request for comment. The senators requested responses by Sept. 9.