The agency is drafting a proposal to help ensure the tests work as intended and are accurate, according to the people. The people wouldn’t provide the timing for releasing the proposal.

The activity comes after a bill in Congress to more tightly regulate the tests stalled. An agency proposal, however, is likely to face heavy opposition from the $10 billion-a-year industry that develops and runs the tests and has thwarted earlier regulatory pushes.

“If the regulations become too burdensome, this could limit a lab’s ability to provide those tests,” said Shannon Haymond, president of the American Association for Clinical Chemistry, which represents 8,000 lab professionals.

At issue are tests on blood, urine and other specimens that labs at academic medical centers and public companies develop and run on their own, rather than selling for others to use. Many Americans depend on the tests to learn if they have the flu or low levels of testosterone, or if a baby might be born with a developmental disorder, for example.

Mayo Clinic, Labcorp and Quest Diagnostics are among those offering the lab-developed tests. The tests make up about half of all those conducted in professional labs, according to Grand View Research.

During the pandemic, many people in the U.S. found out whether they had Covid-19 from lab-developed PCR tests regulated by the FDA.

Yet the agency hasn’t usually regulated the tests, unlike traditional lab tests, FDA-cleared machines or kits that companies sell nationwide, prompting concerns that people could be making important health decisions based on questionable test results.

The FDA has said some labs aren’t careful enough about whether their tests can really show what they claim and whether they are resulting in too many false positives or false negatives.

The agencyhas pointed to studies that show scientistscould confirm positive results from tests for DiGeorge syndrome, a chromosomal abnormality that can lead to heart defects and developmental delays, 30% of the time—meaning 7 out of 10 women who took the test and got a positive result might have been given inaccurate information.

The nonprofit Friends of Cancer Research has sponsored studies finding that results from different lab-developed cancer-related tests vary widely. That can be a problem for drugmakers trying to evaluate whether experimental drugs work safely, or doctors wondering if their patients would benefit from certain therapies, the group has said.

For nearly a decade, the FDAhas pushed Congress to pass a new legal plan for overseeing lab-developed tests, including requiring certain tests—deemed high-risk because they could cause serious harm or death if the results were wrong—to get FDA approval before going into use.

Academic medical centers and other opponents have pushed back, arguing the legislation that FDA favors would discourage innovation, duplicate the work of other agencies that already regulate the labs, and add costs without improving patient safety.

Some say the FDA doesn’t have the legal authority to regulate lab-developed tests on its own, without legislation.

“There would certainly be talk about lawsuits,” said Jonathan Genzen, chief medical officer at ARUP Laboratories, a company owned by the University of Utah that processes more than 70,000 specimens daily.

Quest referred questions to the American Clinical Laboratory Association, a trade group.A representative of that group said it is neutral on the legislation, but would prefer legislation to FDA issuing its own regulations. Labcorp didn’t provide comment.

The FDA has said that it has clear authority to regulate the tests, but that the proposed legislative solution, which it still supports, would help patients and wouldn’t duplicate the work of other agencies.