EVALUATION OF A COLLOIDAL METAL IMMUNOASSAY DEVICE FOR THE DETECTION OF TRICYCLIC ANTIDEPRESSANTS IN URINE

Background: The sensitivity and selectivity of a colloidal metal immun oassay device (Triage(R) Plus TCA) which is designed for the rapid det ection 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 a dding known amounts of amitriptyline, nortriptyline, imipramine, desip ramine, doxepin and desmethyl-doxepin to drug free urine. The selectiv ity of the assay was determined by adding known concentrations of 32 d rugs 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 obta ined with thin layer chromatography and high performance liquid chroma tography. Results: Triage Plus yielded a positive response to gravimet rically 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, desipramin e and doxepin. Other tricyclic antidepressant drugs, clomipramine and protriptyline were positive at 1000 ng/mL. Significant cross-reactivit y was observed only with cyclobenzaprine at 1000 ng/mL. No significant cross reactivity was found at 1.0 g/L for 32 drugs commonly encounter ed in emergency department admissions. A 95% (70/74) agreement of posi tive tricyclic antidepressant results was observed between Triage Plus and thin layer chromatography. Discordant mines were found by high pe rformance liquid chromatography to contain tricyclic antidepressant co ncentrations below the cut-off value of the colloidal metal assay. Con clusion: Triage Plus was found to be an accurate device for the detect ion of tricyclic antidepressants in urine at the stated cut-off value of 1000 ng/mL tricyclic antidepressant. With the exception of cycloben zaprine, significant cross-reactivity was not observed with other drug s commonly encountered in emergency department admissions.