an acid or base will alter the pH
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.
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