Cross-reactivity of nefopam and its metabolites on three different urine benzodiazepines immunoassay screenings: A comparative study

Abstract

Summary Objectives To highlight an analytical interference involving nefopam and its metabolites on urinary benzodiazepine screening with Enzyme Multiplied Immunoassay Technique (EMIT) Atellica CH from Siemens Healthineers, and to evaluate two other immunoassays: MULTIGENT on Architect from Abbott Diagnostics and Cloned Enzyme Donor Immunoassay (CEDIA) Thermo Fisher kits on Cobas from Roche Diagnostics. Case/methods An analytical interference was suspected for a 58-year-old-woman hospitalized for unexplained malaise. The urinary EMIT Atellica benzodiazepine immunoassay was positive. Screenings by liquid chromatography coupled with diode array detector (LC-DAD) and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) identified nefopam and metabolites but no benzodiazepine. Drug-free urine has been spiked at different concentrations of nefopam (187,5–3000 μg/L) and tested on EMIT Atellica assay. Three urines from nefopam-treated patients and two negative controls have been selected to assess this cross-reactivity. Nefopam quantification has been performed by LC-DAD. Different immunoassays were evaluated: EMIT on Atellica, MULTIGENT on Architect and CEDIA on Cobas. Results Drug-free urines spiked with nefopam were negative on EMIT Atellica immunoassay. The interference observed was confirmed for nefopam-treated patients (2/3) on EMIT Architect. For one patient, an interference was observed with a low concentration of nefopam ( Discussion/conclusion Comparison of three immunoassay techniques revealed a heterogeneity of the interference. Nefopam metabolites may be responsible for this cross-reactivity, suggesting the importance of testing them during the kits evaluation phase. This study highlights the need to confirm immunoassay results by more specific techniques.