In the case of a drug test, the window of detection refers to how long the drug is present in the person above the cut-off level, usually express as ng/mL (nanograms per milliliter). The window of detection can vary in two ways: First, it varies based on the type of specimen being tested (i.e. urine versus hair). Second, it can also vary based on the specific drug being tested, as some drugs are metabolized in the body faster than others. Let’s delve into both these areas.
The cut-off level refers to the sensitivity of the drug test. It’s the dividing line between a positive and negative test result.
Drug testing can be performed on various specimen types including oral fluid, urine, hair, nail, sweat and breath. The window of detection for each specimen type varies greatly as the table below indicates. For example, if your client is trying to demonstrate sobriety two weeks ago, then a hair test is probably the best fit.
Just like with the specimen type, the window of detection also varies by the drug being tested. Let’s take a basic 5-drug urine test as an example. In the table below, you can see that each drug is detectable for different time periods, with marijuana being the longest for chronic heavy use.