Toxicology – Screens
Immunoassay screens are typically the first line assays because they can produce positive /negative results within 24/48 hours. However, immunoassays have limitations. Most immunoassay screens detect the presence of a drug class (e.g. opioids) and not the individual drug (e.g. hydromorphone), so assessing compliance can be challenging. Moreover, because they are designed to cross-react with numerous drugs within a drug class, the antibodies also can cross-react with drugs outside that drug class—particularly if the drugs are present at high enough concentrations—thereby producing false positive results. Several studies have suggested that negative screening results also should be confirmed by LC-MS/MS or GC-MS to achieve adequate sensitivity
Toxicology – Confirmation
UDT is performed via a two-step process: an initial drug screen followed by confirmation or definitive testing for the drugs/drug classes. Most immunoassay screens detect the presence of a drug class (e.g. opioids) and not the individual drug (e.g. hydromorphone), so further testing might be necessary. Due to these limitations, more specific, definitive testing such as liquid chromatography tandem mass spectrometry (LC-MS/MS) should be used also.Due to mass spectrometry’s superior sensitivity and specificity, many laboratorians have advocated it as the first line testing methodology, particularly for frequently prescribed drugs such as opioids and benzodiazepines. Quantitative mass spectrometry also can provide information on the presence of particular metabolites, assisting in detecting urine adulteration or determining the parent compound(s) ingested.
Toxicology - Services