Screening
In the acute overdose situation, most toxicologists suggest that benzodiazepine (BZD) screening is not appropriate.
Immunoassay screening tests for BZDs that are typically used in emergency care settings have many false-positive and false-negative results; hence, their use should be discouraged. Most screening tests for BZDs detect only certain metabolites of BZDs (namely, desmethyldiazepam or oxazepam), but many BZDs are metabolized to other substances and so are not routinely detected.[30] Negative screening tests do not therefore exclude BZD overdose. Furthermore, because the half-life of many BZDs or their metabolites is long, a positive screening test may fail to differentiate between BZD use at some time in the past (sometimes even weeks previously) and acute overdose.
When legal issues are involved, rather than in the acute overdose setting - for example, a driver suspected of an offense of "driving under the influence" or BZD abuse - screening BZD tests are based on colorimetric immunoassay and can be performed on either serum or urine samples. A positive screening test should be followed by a sample sent to a National Institute on Drug Abuse (NIDA)-qualified laboratory for a confirmatory test. These are usually performed on urine samples. The NIDA cut-off level for a positive test for BZDs in these cases is 200 nanograms/mL. A minimum level is allowed to protect people who are accidentally exposed to small quantities, such as a nurse who spills tiny quantities on her hands and absorbs a small amount. Only if the confirmatory test is positive should the patient be considered to have a positive test.[2]
Use of this content is subject to our disclaimer