Specimen validity testing (SVT)

• How would a drug test be evaluated when nitrites are 199 mg/mL?

  The nitrite result would be negative, as this level would not interfere with our testing process. The drug test(s) ordered would be conducted and reported following standard operating procedures. 

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• Is the nitrite test threshold based on body functions, or does it allow for infection, food ingestion with high nitrates, and water consumption with high nitrites?

  The nitrite or oxidant threshold level established by the federal government is 200 mg/mL. This is based on the level at which a drug screen may be impacted by this type of adulterant and is higher than what would be expected from normal physiological processes. Nitrites or other oxidants > = 200 mg/mL are reported as “Invalid”. Specimens with nitrite levels > = 500 mg/mL are reported as “Adulterated”. 

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• What tests are included in the Labcorp SVT panel?

  At a minimum, the SVT panel includes testing for creatinine; a creatinine < 20 mg/dL reflexes to a specific gravity test. Results of both creatinine and specific gravity are used to identify dilute, substituted or invalid specimens. Tests for pH and nitrite can also be added to a panel, and are used to assess whether the physiological parameters of the collected specimen are in the expected range. 

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• Does the lab conduct SVT before screening for drugs?

  No, specimen validity testing is performed simultaneously with the initial drug screens. Depending upon the drug screen and the specimen validity results, the laboratory will release (1) both the drug screen and the specimen validity test results, (2) the specimen validity test results only, or (3) the drug screen results only. 

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• What is specimen validity testing?

  Specimen validity testing (SVT) is performed on a urine drug screen specimen to detect substitution, adulteration, or dilution. See the Drugs of Abuse Reference Guide for additional information on SVT. Use of a Medical Review Officer is recommended to evaluate out of range SVT results.

  • Substitution - Submission of a specimen that is not characteristic of human urine. Typically, this may be water or water with salt in it and is identified by extreme creatinine and specific gravity results.
  • Adulteration - Adding a substance to a specimen after it has been collected. The product added is designed to mask the presence of, or chemically destroy, the drug or drug metabolite that the specimen may contain. An adulterant product may be added with the intention of adversely affecting the testing reagents.
  • Dilution - Result of ingestion of large amounts of water typically just before urine donation or as a result of physiological conditions. If drug/metabolites are diluted to a concentration below the initial test cutoff, a dilute urine may result in a false negative.

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