What Urine Testing Doesn’t Tell You

Much of drug testing, particularly in the criminal justice arena, relies on classic urine testing. These tests are the historical go-to tests because they are quick and can check for a large number of illicit and abused substances. However, there is a tendency to over-interpret the results of a randomly collected classic urine drug test. Here are four commonly asked questions that a urine test cannot answer.
  • When was the drug used? The window of detection in urine varies considerably by drug, and urine testing can only give an approximate time of use. The results are also affected by how much was used, the frequency of use and how concentrated or dilute the urine is. For example, without additional information, a positive test for marijuana could indicate use anywhere from two days to five weeks ago.
  • How much of the drug was used, or if alcohol, what was the patient’s blood alcohol level? It is impossible to tell how much of a substance was used with urine testing. A higher result could mean either that more of the drug was taken or it could mean that it was taken more recently—there is no way to know which is true. Regarding testing for alcohol, blood alcohol levels do not correlate to the levels of the alcohol metabolites that can be found in urine. It is also not possible to tell what type of alcohol was consumed.
  • Was the patient using the drug as prescribed? Urine is not the right matrix to answer this question; you need to use blood or oral fluid to get a sense of whether the patient’s drug level matches what would be expected for a given prescription. This is why our CORE oral fluid offering, which can address this question without increasing cost and without using needles, is such an important innovation for our industry.
  • Is the patient addicted to or dependent on this drug? This question asks for a clinical diagnosis rather than a biochemical result. Although frequent positive results may suggest a dependency problem, only a properly trained clinician can make that diagnosis.
Despite its limitations, urine testing can be an extremely effective and cost-efficient way to check on patient behavior. But it is also important to remember that this information is just one part of a larger picture.