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Monthly UDT positivity rates and 95% confidence interval (CI) values for cocaine (light blue line), methamphetamine (orange line), heroin (yellow line), and prescription opioids (i.e., hydrocodone, hydromorphone, oxycodone and oxymorphone without a reported prescription, red line) in fentanyl-positive specimens collected from 2013-2023. Positivity rates were estimated using logistic regression (see Methods).