This story was originally published July 31, 2014.

Thousands of tests on the market take advantage of a legal loophole that exempts them from requirements that their makers prove they correctly identify what they claim to, forcing doctors and patients to decide which tests are legitimate.

FDA commissioner Margaret Hamburg said during a news conference that her agency was aware of faulty tests, such as those that led cancer patients to receive inappropriate treatment and those for autism.

“Inaccurate test results could cause patients to seek unnecessary treatment or delay and sometimes forgo treatment altogether,’’ said Hamburg.

Oversight will be phased in over nine years, with the first batch of highest-risk tests subject to FDA review a year after the proposed rules are finalized. Some of these tests are developed in Cambridge and Greater Boston’s thriving biotech industry.

At issue are what’s known as laboratory developed tests, or LDTs, which include many of the genetic tests developed since the human genome was first sequenced a decade ago. As long as these tests are distributed through physicians and not directly to consumers, they can be sold without FDA approval.

While lab-developed tests provide great promise for better treatment of patients, some medical specialists say, they can create confusion for consumers, who may not know which tests have been proven accurate and won FDA approval and which ones haven’t.

Earlier this year, the U.S. Centers for Disease Control and Prevention issued a warning to doctors not to use Lyme disease diagnostic tests that were not approved by the FDA. Also of concern are the increasing use of tests to identify genes in cancer patients in an effort to guide doctors in choosing appropriate treatment.

Debate over laboratory developed tests dates to the 1990s, but previous efforts at FDA oversight have been met with sustained opposition from the laboratory community, which says it will stifle innovation, causing delays in bringing valuable tests to patients, and be too costly.

The FDA will not subject all LDTs to oversight, agency officials said, but just the riskiest ones. It will exempt some tests, such as those created in a hospital for patients in that hospital, and those for rare diseases and for conditions for which no comparable FDA-reviewed test exists.

Alan Mertz, president of the American Clinical Laboratory Association, an industry group, said the tests are already overseen by other regulatory agencies and FDA oversight would result in patient harm.

“We’ve seen an explosion of innovation in laboratory diagnostics that has allowed labs to diagnose and measure disease with an accuracy and precision never before possible,’’ Mertz said in a statement. “This has changed how the medical world views and treats everything from rare diseases to infectious disease to cancer.”

Senator Edward Markey, a Massachusetts Democrat, applauded the FDA for releasing the “long-overdue” proposed guidance. He, along with a group of other senators, recently sent the FDA a letter urging it to oversee the tests.

“I am pleased that OMB and FDA have responded to my call to finally release draft guidance to provide clarity in the oversight of laboratory developed diagnostic tests,” Markey said.