Urinary tricyclic antidepressant screening: comparison of results obtained with Abbott FPIA reagents and Syva EIA reagents.

Human urine was tested for tricyclic antidepressants with fluorescence polarization immunoassay (FPIA) reagents on Abbott's ADx system and with EIA reagents on Syva's ETS system. A 75-ng/mL imipramine calibrator cutoff was used with the ADx system and a 300-ng/mL nortriptyline calibrator cutoff with the ETS system. The ETS system was adapted to analyze tricyclic antidepressant (TCA) samples using the Syva Emittox serum TCA assay. Negative urine was spiked with various tricyclic and tetracyclic antidepressants, phenothiazines, and other medications with potential to interfere with the assays. Verification of samples was performed by thin-layer chromatography and gas chromatography/mass spectrometry. The different compounds were added to urine at concentrations of 200, 400 and 1,000 ng/mL. At 1,000 ng/mL all TCA compounds tested gave positive results with the ADx and ETS systems. However, some non-TCA medications spiked at 1,000 ng/mL gave false positive results with both systems. The tetracyclic antidepressants did not cross-react and gave negative results. Clomipramine-spiked urine at 400 ng/mL yielded a false negative result on the ETS system.