An Introduction to Testing for Drugs of Abuse. William E. Schreiber

Normal human urine does not contain oxidants above the assay cut‐off, and increased values may indicate adulteration Nitrite Nitrite is not detectable in normal urine samples, but it may be elevated in patients with a urinary tract infection. High levels of nitrite may indicate an adulterated sample Chromate Chromate is an effective oxidizing agent, and it is not normally present in human urine. A positive test suggests that the urine sample has been adulterated Aldehyde Glutaraldehyde and other aldehydes are not present in normal human urine. A positive test suggests that the sample has been adulterated

      Interpretation of Specimen Validity Testing

The Substance Abuse and Mental Health Services Administration (SAMHSA) has developed criteria for specimen validity in workplace drug testing programs. Dilute and substituted specimens are identified by comparing the values for creatinine and specific gravity (Table 3.1). To label a specimen as adulterated, an abnormal pH or the presence of a known adulterant is required (Table 3.2).

Table 3.1 Substance Abuse and Mental Health Services Administration criteria for labeling a urine specimen as dilute or substituted.^a

Test	Dilute	Substituted
Creatinine	≥2 and <20 mg/dL	<2 mg/dL
Specific gravity	>1.001 and <1.003	≤1.001 OR ≥1.020

      ^a Both criteria (creatinine and specific gravity) must be met.

Table 3.2 Substance Abuse and Mental Health Services Administration criteria for labeling a urine specimen as adulterated.^a

Test	Adulterated
pH	<3.0
	≥11.0
Nitrite	≥500 μg/mL
Chromium (VI)	Present
Glutaraldehyde	Present

      ^a Any one criterion is adequate. Depending on how samples are tested, other adulterants may be detected as well.

Table 3.3 Substance Abuse and Mental Health Services Administration criteria for labeling a urine specimen as invalid.^a

pH value ≥3.0 and <4.5 and ≥9.0 and <11.0

Nitrite value ≥200 and <500 μg/mL

Inconsistency between creatinine and specific gravity

Interference in a screening or confirmatory assay

Presence of oxidizing compounds

Possible presence of:

chromium (VI)halogen (e.g., iodide)surfactant (e.g., soap)

Physical appearance of specimen

      ^a Individual laboratories may use different or additional criteria.

Specimens can also be deemed invalid in a number of situations (Table 3.3). An invalid result may indicate specimen tampering, but other explanations are possible. A review of the patient's history and consultation with the laboratory may clarify the situation.

Further Reading

      Articles

      1 Allen, K.R. (2011). Screening for drugs of abuse: which matrix, oral fluid or urine? Ann. Clin. Biochem. 48: 531–541.

      2 Bosker, W.M. and Huestis, M.A. (2009). Oral fluid testing for drugs of abuse. Clin. Chem. 55: 1910–1931.

      3 Cooper, G.A.A., Kronstrand, R., and Kintz, P. (2012). Society of hair testing guidelines for drug testing in hair. Forensic Sci. Int. 218: 20–24.

      4 Dasgupta, A. (2007). The effects of adulterants and selected ingested compounds on drugs‐of‐abuse testing in urine. Am. J. Clin. Pathol. 128: 491–503.

      5 Verstraete, A.G. (2004). Detection times of drugs of abuse in blood, urine and oral fluid. Ther. Drug Monit. 26: 200–205.

      Book chapter

      1 Garg, U. and Cooley, C. (2019). Testing of drugs of abuse in oral fluid, sweat, hair, and nail: analytical, interpretative, and specimen adulteration issues. In: Critical Issues in Alcohol and Drugs of Abuse Testing, 2nd Edition (ed. A. Dasgupta), 405–427. Academic Press.

      Technical assistance publication

      1 Clinical Drug Testing in Primary Care (2012). HHS Publication No. (SMA) 12‐4668. Rockville, MD: Substance Abuse and Mental Health Services Administration. https://store.samhsa.gov/sites/default/files/d7/priv/sma12‐4668.pdf.