Quetiapine cross-reactivity among three tricyclic antidepressant immunoassays.
Quetiapine is an atypical antipsychotic agent with structural similarities to the tricyclic antidepressants (TCA). We report a case of quetiapine overdose that was initially clinically similar to that of a TCA overdose and caused a false-positive TCA immunoassay. We then analyzed three common TCA immunoassays [Microgenics (formerly Diagnostic Reagents, Inc.) Tricyclics Serum Tox EIA Assay, Syva RapidTest d.a.u., and Biosite Triage Panel for Drugs of Abuse] with quetiapine in solution as well as urine from both an overdose patient and a therapeutic patient. There was significant variation of the cutoff of false-positivity in all three immunoassays. Both the Syva and Microgenics immunoassays tested positive in both the overdose and therapeutic samples and were positive at urine levels of 100 microg/mL and 10 microg/mL, respectively. The Triage immunoassay was negative in solutions up to 1000 microg/mL and negative in both the therapeutic and overdose urine samples. Quetiapine may cause false-positive TCA immunoassay with both therapeutic use and in overdose. Significant variation exists between immunoassays to detect quetiapine as a false-positive test.
Department of Emergency Medicine, Oregon Health and Science University, Portland, Oregon 97201-3098, USA. hendriro@ohsu.edu
Robert G
RG
Hendrickson
Anthony P
AP
Morocco
D000328:Adult; D000918:Antibody Specificity; D000929:Antidepressive Agents, Tricyclic / Q000737:chemistry / Q000276:immunology* / Q000652:urine; D014150:Antipsychotic Agents / Q000276:immunology* / Q000506:poisoning / Q000652:urine; D002849:Chromatography, Gas; D003429:Cross Reactions; D003987:Dibenzothiazepines / Q000276:immunology* / Q000506:poisoning / Q000652:urine; D062787:Drug Overdose; D004562:Electrocardiography; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007118:Immunoassay; D008133:Long QT Syndrome / Q000139:chemically induced; D000069348:Quetiapine Fumarate; D013406:Suicide, Attempted
D000929:Antidepressive Agents, Tricyclic; D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D000069348:Quetiapine Fumarate