Improved screening sensitivity does not make a negative screen conclusive.
An evaluation of the Roche BNZ2 immunoassay found improved detection of lorazepam- and clonazepam-related exposure compared with an earlier assay. Nevertheless, it missed twenty-seven percent of specimens positive by the study’s LC-MS/MS testing.
The evaluation included emergency-department and compliance-monitoring specimens. Better cross-reactivity for relevant metabolites helped the newer screen, but did not close the detection gap. A targeted LC-MS/MS panel can itself omit synthetic benzodiazepines or other analytes. In laboratory review, request the analyte list and reporting thresholds for both stages before treating a disagreement as proof that one specimen contained no benzodiazepine.
Performance depended on the studied populations, cutoffs and analytes. Definitive panels also have scope limits and may not include every emerging compound. The reported percentage is not a universal false-negative rate for every laboratory.
Identify the exact assay, cutoff and confirmation panel. A negative result does not exclude a poorly detected benzodiazepine or metabolite. In a case opinion, distinguish screening capability from analytical identification and avoid treating either method’s panel as evidence about substances it never tested.
Source: PMC11262176, supplied full-text paper. Findings are paraphrased; forensic implications are an interpretation.
Related: Diazepam Worsened Activity in Some Immature Brain Slices but Improved Older Slices.