The terms “screening test” and “confirmation test” are thrown around a lot in drug testing so it is important that you feel confident in what each means. We will go over the two terms here to make sure you fully understand what they mean, and how they work.
When tests are referred to as being screens (or confirmations) what is being specified is the type of technology used to obtain the information, as well as the kind of information that is obtained. So, how do they do the testing, and what kind of results you get, depends on whether it’s referred to as a screen or a confirmation.
A screen test uses immunoassay technology, which uses antibodies binding to antigens to indicate whether a drug, or its metabolite (whichever is being tested for) is present in the sample at, or above the testing threshold.
Whether the screen is occurring on site using a rapid test (the drug test that shows you a positive or negative result right away) or in a laboratory setting using laboratory instrumentation (EIA,EMIT), the technology is the same.
The results of this kind of testing will only give you qualitative information. This means that there will be no information about a specific level for what is being tested. Rather, a positive will indicate the drug or metabolite being tested for is detected in the sample on, or above, the cutoff of level. A negative will mean it is below this level (which could mean it is not present at all, OR could mean it is present but simply lower then the cut-off for the test).
Once a specimen has been screened non-negative for a drug or metabolite, it will be sent on for further testing, this is the confirmation test.
A confirmation test can ONLY be done within a laboratory as it uses very sensitive analytical methodology with equipment such as LC-MS (liquid chromatography-mass spectrometry) or GC-MS (gas chromatography-mass spectrometry). These machines combine two types of analytical chemistry techniques, the first to separate the specimen into parts, and the second to analyze the mass of those parts.
This type of testing is far more sensitive then the screening test and the results which are received will give definitive information about the concentration levels of specific drugs and/or their metabolites. These will be quantitative results, giving you specific amounts of the drug or metabolite found; this absolute nature of confirmation tests is what makes them defensible in court.
The laboratory sends the confirmation test result to a Medical Review Office for quality assurance and a chance for the donor to have their interview with the MRO. When they have completed their review of the results the MRO will verify the result and release it to the appropriate parties.