Laboratory Developed Tests: Not All Tests are Created Equal

It seems there is a test for every medical problem. Demand is high for better, faster, more sensitive tests, but did you know some of these tests may not be useful or even approved by the FDA?

This is especially true of laboratory developed tests or LDTs. Some examples of LDTs are tests for genes or proteins linked to rare diseases or cancer. LDTs were intended to be simple new tests or variations designed by specific laboratories for use in their facilities. For instance, a hospital that specializes in treatment of rare cancers might develop a genetic test to identify patients with these rare cancers. The genetic test would be used only in that hospital and only for patients receiving treatment in the hospital.

LDTs were not intended to be marketed or used outside of a single facility and so FDA decided not to regulate LDTs.  Since FDA isn’t regulating them, the FDA does not require extensive testing or independent evaluation of the proof that LDTs work, which they require for most medical tests.[1] However, a growing number of companies are widely advertising LDTs as diagnostic tools and neither doctors nor patients realize the LDTs are not proven for this purpose. Doctors send patient samples to a company who performs their LDT and sends the doctor results to be used to make a diagnosis. Doctors may not know how to correctly interpret results from new tests, putting patients at risk for misdiagnosis.

Two Examples of Questionable Tests:

The standard test for Lyme disease is known to be inaccurate.[2] In 2011, a company produced a new test for Lyme disease that it claims is more  accurate, and doctors and patients assume it is.[3] Unfortunately, there is no published data proving the accuracy of the new test.

The  usual test used to diagnose prostate cancer  measures prostate specific antigen (PSA), but experts criticize the PSA test because it identifies cancers that are unlikely to ever harm the patient. A new genetic test can better identify cancers that are more aggressive and could be fatal. However, 19% of men who are categorized as having low risk cancers based on the new test die of prostate cancer — making the new test too inaccurate to help men decide which cancers require treatment. With a high price tag (the test costs $3400) and low confidence in the test, this LDT seems to be an expensive but mostly useless test in terms of helping patients and their doctors make treatment decisions.[4]

Here are some points to think about when deciding if a test will be useful in diagnosing or treating disease:

  • Do not get a test without consulting a doctor you trust.
  • Ask your doctor if the test is proven to work in published studies or if it is a new test that might not yet be proven. If a test is only performed by one facility, it might not be widely accepted or validated.
  • Do not get a test unless there is a good reason (family history, you’re experiencing symptoms that are only related to a particular disease). If you think you have a particular illness, talk to a doctor FIRST instead of insisting on a test. There might be another explanation.
  • Before getting a test, ask your doctor if the results of the test would influence your treatment. If the answer is no, it’s an unnecessary test.  CLICK HERE for more information about the Choosing Wisely campaign to avoid unnecessary medical tests.

All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff. 

  1. Food and Drug Administration (2010) Accessed 6/21/2013
  2. Center for Disease Control (2011) Accessed 6/21/2013.
  3. Advanced Laboratory Services (2011) Accessed 6/21/2013
  4. New York Times, May 8, 2013. Accessed 6/21/2013