But Granger also noted that spit tests will never replace blood tests. Levels of certain enzymes, proteins or hormones in blood might not have the same correlation in spit. Other times doctors need to test a full panel of different components found in blood, which can't be done with spit.
"People want to measure things in saliva because they want to use it for a surrogate marker for what's in your blood," Granger said. "That is not always the case."