False positive urine drug screens.

Area of Science:

• Clinical Toxicology
• Analytical Chemistry
• Pharmacology

Background:

• Immunoassay-based urine drug screens are common in clinical toxicology for rapid, automated testing.
• Antibody cross-reactivity in immunoassays can lead to false-positive results, impacting patient care, employment, and legal cases.
• Previous literature on immunoassay interferences requires updating to reflect recent findings.

Purpose of the Study:

• To review and update literature on false-positive interferences in immunoassay urine drug screens from 2013 to 2024.
• To analyze interferences across common drug classes, including opioids, amphetamines, and cannabinoids.
• To provide current reference data on interferents and emphasize the limitations of presumptive testing.

Main Methods:

• Systematic review of published studies on false-positive interferences in urine drug screens.
• Inclusion of 61 studies from 569 retrieved publications meeting specific criteria.
• Categorization of reports by level of evidence, from case reports to controlled experiments.

Main Results:

• Identified and categorized numerous false-positive interferences across various drug classes screened by immunoassay.
• Demonstrated that despite advancements, immunoassay drug screens remain presumptive and susceptible to cross-reactivity.
• Highlighted the continued prevalence of interferences requiring confirmation by orthogonal methods.

Conclusions:

• Immunoassay drug screens are presumptive and necessitate confirmation by techniques like GC-MS or LC-MS/MS.
• Updated reference data on interferents is crucial for accurate interpretation of drug screen results.
• Enhanced laboratorian-clinician communication and ongoing education on assay limitations are vital for preventing misinterpretations and ensuring appropriate clinical decisions.