Williams v Quest/Athena struck a nerve with the genetic testing community by probing what the standard of care is and ought to be for variant classification.
The decision means the ruling by an appeals court that Mayo did not infringe on Athena's patent on a method of diagnosing myasthenia gravis will stand.
The development is a positive for plaintiff Amy Williams, who has said she hopes her lawsuit will spur greater accountability and transparency among genetic testing labs.
Though the South Carolina Supreme Court said Quest was a healthcare provider, Williams can try to keep her case alive by arguing she's alleging ordinary negligence.
A federal court dismissed the litigation saying that the patent at the center of the dispute applies routine and conventional techniques to a law of nature.
In Williams v Quest/Athena, a federal district court judge has asked the highest state court to clarify if a genetic testing lab is a licensed healthcare provider.