The Laboratory Testing Process

The Laboratory Testing Process

The initial test is a screening test which identifies a range of illicit and therapeutic substances. Screening is performed by immunoassay on the Hitachi 911 using Cedia reagents and methodology. Routine screening involves the testing of the following classes:

Testing can also be performed for additional drugs, including alcohol.

If the initial screening test is positive, a second unopened sample aliquotted from the original specimen is tested by a different method for confirmation of the initial result.

Confirmation of drug classes detected by Immunoassay is performed by gas Chromatography/Mass Spectrometry (GC/MS).

The presence of each drug or metabolite is tested for at or above a predefined cut-off level (see list below). These levels are dictated by International Standards for urine drug testing and defined in the Australian/New Zealand Standard AS/NZS 4308:2001. The “cut-off” levels are established because the aim of workplace testing is usually to identify significant residues of the targeted drug, not minute traces. For a result to be “positive”, the amount of the drug detected must be at or above the “cut-off” level. If a drug is detected but the level is below the “cut-off” the result will be negative. The “cut-off” levels for some classes differ for screening and confirmation. This is due to the non-specific nature of the screening assay versus the highly specific nature of the GC/MS confirmation.