Published: Journal of Analytical Toxicology, ISSN 0146-4760, Volume 26, Number 7, October 2002, pp. 424-429

Evaluation of Freezing Point Depression Osmolality for Classifying Random Urine Specimens Defined as Substituted Under HHS/DOT Criteria
Janine Denis Cook[1], Mark W. Hannon, Sr.[2], Tamdan Vo[3], and Yale H. Caplan[4]
[1]University of Maryland, Baltimore, Maryland;
[2]Quest Diagnostics Incorporated, Wallingford, Connecticut;
[3]Montgomery General Hospital, Olney, Maryland; and
[4]National Scientific Services, Baltimore, Maryland

This controlled hydration study was designed to validate the substitution criteria used by the Substance Abuse and Mental Health Services Administration (SAMHSA) to classify a workplace urine specimen as inconsistent with normal human urine. Study participants (n = 56) ingested at least 80 oz (2370 mL) of fluid over a 6-h period, 40 oz during the first 3 h (DOT hydration protocol) and 40 oz during the second 3-h period. Urine specimens (n = 498) were collected upon awakening, just prior to hydration, at the end of each hour of the 6-h test period, and upon awakening the next day. No urine specimen satisfied the paired substitution criteria of urine creatinine ≤ 5.0 mg/dL and specific gravity ≤ 1.001 or ≥ 1.020. Seventy-three percent of the participants produced at least one specimen meeting the criteria for dilute urine: urine creatinine < 20.0 mg/dL and specific gravity < 1.003. Fifty-five percent of the participants produced at least one dilute urine specimen during the first 3 h of hydration. In conclusion, this controlled hydration study supports the criteria set by SAMHSA for classifying a specimen as substituted (inconsistent with normal human urine).

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