Quetiapine-Associated False-Positive Results on Urine Drug Screens
Quetiapine can cause false-positive urine drug screen results on some immunoassay panels due to cross-reactivity, with confirmatory testing typically resolving the discrepancy. [1-3]
Mechanism: Immunoassay Cross-Reactivity
Urine drug screen immunoassays are susceptible to cross-reactivity from structurally related drugs, which can yield a presumptive “positive” that does not reflect the presence of the target drug on confirmatory testing. [1]
Evidence of Quetiapine Causing False Positives
Quetiapine has been reported to cause false-positive results on urine ketamine immunoassays in case reports, with confirmation testing showing false positivity. [3]
Quetiapine has been reported among medications associated with immunoassay interference in real-world performance evaluations, where confirmation by LC-MS/MS reduced apparent positives substantially. [1]
Confirmation Testing Requirement
When an immunoassay result is unexpected, confirmation with a more specific method such as LC-MS/MS or GC-MS is required to determine true drug presence and to identify immunoassay false positives. [1]
Clinical Interpretation Approach
Unexpected immunoassay positives should be interpreted as presumptive until confirmatory testing is available. [1]
Medication reconciliation should be performed for all active prescriptions prior to concluding that an immunoassay result is true. [1]
Common Pitfalls to Avoid
Relying on the initial immunoassay screen without confirmation increases the likelihood of misclassification due to cross-reactivity. [1]
Recommended Next Steps After a Positive Screen
Obtain confirmatory testing (LC-MS/MS or GC-MS) for results that conflict with the medication history. [1,3]
Document the quetiapine dose and timing of last administration when interpreting confirmatory results and resolving discrepancies. [1,3]