Evaluation of a Colloidal Metal Immunoassay Device for the Detection of Tricyclic Antidepressants in Urine

Abstract

Background: The sensitivity and selectivity of a colloidal metal immunoassay device (Triage® Plus TCA) which is designed for the rapid detection of tricyclic antidepressant drugs in urine at a total tricyclic antidepressant concentration of 1000 ng/mL or greater were evaluated. Methods: The sensitivity of the Triage Plus assay was determined by adding known amounts of amitriptyline, nortriptyline, imipramine, desipramine, doxepin and desmethyl-doxepin to drug free urine. The selectivity of the assay was determined by adding known concentrations of 32 drugs or drug metabolites commonly encountered in emergency department admissions to drug free urine. Triage Plus results from clinical urine specimens containing either amitriptyline, nortriptyline, imipramine, desipramine, doxepin and desmethyldoxepin were compared to those obtained with thin layer chromatography and high performance liquid chromatography. Results: Triage Plus yielded a positive response to gravimetrically prepared urines of tricyclic antidepressant at the stated cut-off value (1,000 ng/mL), and at 80% (800 ng/mL) and 50% (500 ng/mL) of the cut-off with amitriptyline, nortriptyline, imipramine, desipramine and doxepin. Other tricyclic antidepressant drugs, clomipramine and protriptyline were positive at 1000 ng/mL. Significant cross-reactivity was observed only with cyclobenzaprine at 1000 ng/mL. No significant cross reactivity was found at 1.0 g/L for 32 drugs commonly encountered in emergency department admissions. A 95% (70/74) agreement of positive tricyclic antidepressant results was observed between Triage Plus and thin layer chromatography. Discordant urines were found by high performance liquid chromatography to contain tricyclic antidepressant concentrations below the cut-off value of the colloidal metal assay. Conclusion: Triage Plus was found to be an accurate device for the detection of tricyclic antidepressants in urine at the stated cut-off value of 1000 ng/mL tricyclic antidepressant. With the exception of cyclobenzaprine, significant cross reactivity was not observed with other drugs commonly encountered in emergency department admissions