Definitive urine drug testing in emergency medicine: Recreational and psychiatric drug findings

Abstract

Introduction

Clinical management of drug-related emergency department (ED) visits relies on available history, toxidrome findings and drug screening. In this study, definitive drug testing is used to assess ED drug prevalence and immunoassay drug screening performance.

Methods

Definitive testing for 116 drugs and metabolites was performed on urine from 400 ED patients, with comparison to immunoassay drug screening.

Results

Definitive testing resulted in 1,350 drug findings with prevalent use of nicotine (63%), cocaine (34%), ∆9 tetrahydrocannabinol (34%), fentanyl (17%), morphine or heroin (11%) and methamphetamine (6%). Forty percent of patients were also positive for antidepressants and 24% positive for antipsychotics. Significant patterns of co-drug use were found for cocaine, fentanyl, morphine and nicotine. Multi-serotonergic drug use was frequent, suggesting a risk for serotonin syndrome. Immunoassay performance showed high false negative rates for benzodiazepines (40%), amphetamines (38%), barbiturates (33%), opiates (25%), methadone (20%) and cocaine (16%), along with inaccuracy in phencyclidine detection. Immunoassay missed 890 of the 1,350 drug findings by definitive testing, due to either high cutoff thresholds or limited testing scope.

Discussion

A high prevalence of drugs use by ED patients is evidenced with frequent co-use of illicit and therapeutic drugs and with potential for unrecognized multi-serotonergic drug interactions. This study also shows the limitations of immunoassay drug testing in both scope and sensitivity, with a high rate of undetected drug use.

Conclusion

The study provides evidence-based support for recommended implementation of definitive drug testing in emergency medicine as a guide to clinical management in drug-related ED visits.