Prevalence of False Negative Results for Hydrocodone in Oral Fluid Toxicology Compared with Urine Toxicology

Saarang Singh, MD, Aakash Shah, MD, Evan Chung, MD, Joseph Valenza, MD

Introduction

• This study aimed to compare the efficacy and reliability between oral fluid and urine studies in hydrocodone drug monitoring programs.  

Methods

• 14 patients taking hydrocodone randomly selected from a Chronic Pain Center. PMP reports were reviewed prior.
• Oral fluid and urine sample results from April to October 2021 were analyzed for each patient. 
• Hydrocodone levels were measured using enzyme-linked immunoassay (ELISA) and liquid chromatography–mass spectrometry (LC/MS).
• Test results were compared to each other to determine sensitivities of each test type.

Methods

• Oral fluid studies had lower sensitivities with ELISA (71.4%) and LC/MS (85.7%) when compared to urine toxicology studies (100% for both)
• Higher rates of false negative results were seen with oral fluid studies
• LC/MS had fewer false negative results compared to ELISA

1. Oral fluid toxicology may result in more false negative results when compared to urine studies.
2. LC/MS could be a more reliable modality in oral fluid testing when compared with ELISA.