What types of laboratory tests are used for drug screening?

As a standard sample type, we use urine-based drug testing. Initial (immunoassay) and confirmatory (gas chromatography-mass spectrometry [GC-MS] tests) are the methods most commonly utilized once the urine sample is provided. Using a combination of both tests allows a high level of sensitivity and specificity and reduces changes for false positives or false negatives.

The immunoassay is performed first and is often used as a screening method. If the immunoassay is negative, no further action is required, and the results are reported as negative. If the sample is non-negative, an additional confirmatory GC-MS analysis is performed on a separate portion the sample to identify individual drug substances or metabolites and quantify the amount of the substance prior to reporting positive drug test results to employers.