Detecting inherited diseases isn’t the only purpose of genetic testing. There is also a field called “pharmacogenetics,” which looks at the role that genetics may play in a person’s response to a particular drug.

For instance, this is important for prescribing the anticlotting agent clopidogrel (Plavix) because as many as 30 percent of people have a genetic variant that prevents their liver from activating this drug. Therefore, they must take a higher dose or a different agent.

Aspirin resistance is another area of testing. Scientists have always wondered why aspirin, which helps reduce the risk of heart attack, is not effective for everyone.

We now know that as much as 45 percent of the population is genetically resistant to aspirin. Aspirin resistance is not yet routinely checked for, but that could change in the near future.

This is also an area that the FDA is watching carefully. The agency warned Inova Genomics Laboratory of Falls Church, Va., for illegally marketing genetic testing that had not been reviewed for this purpose.

The regulators were particularly concerned that patients may use these tests to start or stop taking particular treatments, decisions that they should only make in consultation with their doctor.