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FACP. Colegio de médicos de Tarragona Nº 4305520 / fgcapriles@gmail.com




Tuesday, February 16, 2016

Urine Drug Screen

TAMING THE SRU - February 15, 2016 - By Gillian Beauchamp
"We are all guilty of ordering them in the ED, but do we really know what we’re ordering?
1 literature review looked at 7 different retrospective studies describing a total of 1,405 patients and found the urine drug screen did not affect the management of any of these patients while in the emergency department (Tenenbein M., 2009). However, the data from the UDS can affect a patient’s clinical care outside of the Emergency Department. For example, if a patient requires psychiatric inpatient care, initial knowledge of drug abuse could affect this patient’s etiology of illness or rehabilitation plan.
The UDS in the ED is Qualitative
It’s typically an immunoassay, in which you have a specific antibody designed to attach to a specific antigen (either the drug or a metabolite). You’re going to get a positive or a negative result.
The Positive Result
  • A positive result means that the derivative of the drug tested in the immunoassay was found and reached its threshold of detection.
  • You can assume exposure either to the drug tested, or to a substance with a similar chemical structure that has cross-reacted with the immunoassay.
  • It cannot tell you the specific drug taken or the amount. 
  • It cannot tell you if the drug is causing your patient’s current symptoms, since the UDS often remains positive for a greater duration than any clinical effects of the drug. That suspected overdose causing altered mental status can always still be a head bleed.
The Negative Result
  • A negative result means that the derivative of the drug being tested in the immunoassay was either absent or no longer accumulated enough to reach the threshold for a positive result.
  • This does not mean it or another version of a drug is present. If you suspect drug use, trust your gut."