The Centers for Disease Control and Prevention updated their guidelines earlier this month for prescribing opioids to patients. According to the modified guidelines, the CDC advises that doctors stop testing patients for tetrahyrdocannabinol (THC), the psychoactive ingredient found in marijuana.

AP Photo/Brennan Linsley

A report by the Pain News Network noted that point-of-care urine drug screens have a history of producing false positive and false negative results for a variety of substances, including marijuana. The pain management news source reported in the past that 21 percent of positive results are false and 21 percent of negative results are positive.

The modified guidelines come weeks after Massachusetts Sen. Elizabeth Warren pressed the CDC to explore the “effectiveness of medical marijuana as an alternative to opioids for pain treatment in states where it is legal,” Think Progress reported.