Urine Drug Screens Be Wrong:
110-C Perimeter Park Rd.
Knoxville TN 37922
Urine Drug Screens be Wrong?
short answer is definitely, YES!
The typical medical office urine drug screen (UDS) is what is called
an immuno-assay test system.
In such systems, a urine sample is tested by exposing the
urine sample to protein antibodies which are designed to detect
(indicated by a color change) the presence of certain molecular
structures or parts of molecules.
Therein lies the rub.
A given molecule, for example, tetra-hydro-cannabinol (THC,
the active agent in marijuana), has structural components which, to
an anti-body, look just like other the structures found in other
molecules, such as ibuprofen or the stomach medicine, Prilosec aka
That's right; the anti-bodies designed to detect the
presence of THC, often indicate the presence of THC when in fact THC
is not present, but ibuprofen (e.g. Advil) or Prilosec (omeprazole)
IS!!! That's called a false positive and it occurs with incredible
because ibuprofen, omeprazole and protonix, to name just a few, have
components (say, a couple of methyl groups) that look just like the
same couple of methyl groups in THC; parts of the molecules are the
same, but the total, whole molecule is quite different.
The only way around this is to send in the sample for Mass
Spectroscopy (MS) which has essentially no error, as it determines
the EXACT structure of the WHOLE molecules present in the urine
sample and names them.
It looks at the whole molecule, not just part, like immuno-assay
second problem with the typical medical office UDS has to do with
Some UDS systems are designed to detect as little as 5
nanograms (ng) of say, hydrocodone.
Others only detect 10 nanograms and above.
Some, require 50ng or more. The
cheaper the system, in general, the higher the limits of detection,
as it is harder to detect 5ng than it is 50ng.
If your doctor has a UDS system that only detects 50ng
or more of hydrocodone, and you haven't taken yours since a few
days ago, you'll probably have a negative drug screen because not
enough hydrocodone is present in your urine to be detected by the
system used for detection.
That's called a false negative.
The system says negative, when the drug really is present,
but in too small an amount for the system being used to detect it.
Another example involves the new pain control patch
medications, butrans or buprenorphine, which is placed every week at
one of four body sites.
The medication in the patch is hard to measure.
Almost no UDS systems measure it as an opiate and even most
labs using MS can't detect it unless specifically asked to do so.
Many patients are discharged from their doctor's care
because they are prescribed the butrans patch, they're drug
screened with an office UDS, and it does not show up.
The problem is that the UDS can't measure the low amount of
But most doctors simply don't know this, and the patient
gets discharged for non-compliance.
the whole domain of drug screening is very complex.
That's why only physicians should use these systems as they
should know the issues of false positives and false negatives, as
well as the basic principles of laboratory medicine.
Under no circumstances should lay employers, school
personnel, or court workers (e.g. probation officers) be allowed to
use and interpret UDS systems, as they have no idea what they're
doing and run the risk of mis-interpretation of UDS results, and may
accidently ruin peoples' lives.