The U.S. government is finally on its way to closing one of the health sector’s most controversial loopholes.

Test kits that are sold to hospitals or directly to patients as medical devices are regulated by the Food and Drug Administration, but it does not oversee tests that are designed in a single laboratory with all the samples being sent there. These LDTs, or lab-developed tests, include Myriad Genetics’ breast cancer risk test, the noninvasive prenatal tests for Down syndrome, and tests from the controversial startup Theranos, among others.

Experts say that thousands of these medical diagnostic tests have never been scrutinized for accuracy and reliability. “There’s never been any real regulation at the federal level of whether these lab tests are meaningful,” Hank Greely, director of the Center for Law and the Biosciences at Stanford University, told Fast Company.

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Historically, according to Greely, LDTs have been monitored by the College of American Pathologists—every clinical lab has a pathologist—as well as a statute called CLIA. This helps ensure that labs are treating samples appropriately and sending back the right results.

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This approach may have been sensible enough in past years when labs were small-scale and developing tests for very niche needs. But circumstances have changed. Nowadays, tests are becoming “more complicated, more strange, and more important,” Greely explained. And the sheer number of lab tests has exploded with recent advances in human gene-sequencing.

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“There has been talk of the industry softening its opposition,” said Greely. “But predicting politics is never easy.”