Tuesday, December 3, 2013

Urine Drug Testing Information

Urine drug testing is widely used for testing for opioids and illicit drugs. There are two types of urine drug testing: a screening test and a confirmatory test. The screening test uses an immunoassay to look for the parent drug and/or metabolite. Most UDTs screen for cocaine, marijuana, PCP, opiates, amphetamines, while some also test for benzodiazepines and methadone. The confirmatory urine drug test is done by gas Chromatography/mass spectrometry or high-performance liquid chromatography; this test is highly specific and is typically used when testing for the presence of a specific drug is needed.

Why urine drug testing?
  • - monitor pharmacotherapy compliance;
  • - identify individuals who may be at high risk;
  • - a means of providing documentation to an agreed treatment plan.
Characteristics of urine
  • temperature 90° F to 100 ° F
  • pH 4.5 – 8
  • creatinine concentration > 20 mg/dl
  • specific gravity 1.003 – 1.030

Creatinine adjusted drug levels

The measured drug level is adjusted to the level of creatinine detected and multiplied by 100 mg/dl (patient's directly measured THC level x average creatinine excreted ÷ patient’s directly measured creatinine level = creatinine adjusted drug level).
Medical drug monitoring
Methods of urine drug testing
  1. Immunoassay drug tests
    • clarifies a substance as being present or absent;
    • advantages:
      rapid turn around time;
      high sensitivity;
    • limitations:
  2. Point of care testing
    • commercially available;
    • does not require instrumentation;
    • easy to use;
    • limited number of tests;
    • interpretation subjective;
    • limited or deficient quality control.
  3. POCT testing
    • users of POCT devices should understand limitations;
    • used should be trained;
    • be aware of interferences from chemicals;
    • consider cutoff(s) in selection of device;
    • must use quality control material National Academy of Clinical Biochemistry (NACB).
  4. Confirmatory testing
    • gas chromatography/mass spectrometry (GC/MS):
      - the gold standard;
      - highly specific and sensitive.

Drugs and their metabolites

Drug classDrugDrug and/or metabolite

Interpreting urine drug levels

  • urine drug levels don’t indicate strength of drug being used
  • urine drug levels don’t indicate how frequently the drug is used
  • blood alcohol as a model

Urine drug test report
Drug not detected may be due to the following:

  • patient didn’t take any of the medication;
  • patient has not recently taken any of their medication;
  • patient excretes medication and /or their metabolites at a different rate than normal;
  • the test used was not sensitive enough;
  • clerical error.

Detection times of drugs in urine
Cutoff (ng/ml)Days
Amphetamines1000< 5
Benzoylergamine after street doses of cocaine3002-3
moderate smoker
heavy smoker
chronic smoker


< 28

The urine test is very reliable and is performed at most federally mandated facilities that require drug testing.

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