Citation

Chattergoon DS, Verjee Z, Anderson M, Johnson D, McGuigan MA, Koren G, Ito S. J. Toxicol. Clin. Toxicol. 1998; 36(1-2): 109-113.

Affiliation

Hospital for Sick Children, University of Toronto, Ontario, Canada.

Copyright

(Copyright © 1998, Marcel Dekker)

DOI

unavailable

PMID

9541055

Abstract

BACKGROUND: Drug toxicological screening is commonly used as a diagnostic tool in patients with suspected toxic ingestion. False positive results due to cross-reactive compounds in drug assays may lead to misdiagnosis and mismanagement, especially when child abuse is suspected. CASE REPORT: Two of our patients with history of ingestion of carbamazepine were tested positive on screening with the tricyclic antidepressant immunoassay. The immunoassay's known cross-reactivity for carbamazepine is reportedly as low as 0.3%. Plasma samples of our patients were initially considered positive for tricyclic antidepressants because the cross-reaction of carbamazepine gave tricyclic antidepressant concentrations as imipramine equivalent sufficiently above the assay cut-off point (20 ng/mL). Later, confirmatory urine testing of both patients using high-performance liquid chromatography was negative for tricyclic antidepressants. CONCLUSION: This interference has significant clinical implications, and can be avoided on urine testing using a specific chromatographic assay such as high-performance liquid chromatography.

Language: en