title: Normalization of urinary drug concentrations with specific gravity and creatinine.
abstract: Excessive fluid intake can substantially dilute urinary drug concentrations and result in false-negative reports for drug users. Methods for correction ("normalization") of drug/metabolite concentrations in urine have been utilized by anti-doping laboratories, pain monitoring programs, and in environmental monitoring programs to compensate for excessive hydration, but such procedures have not been used routinely in workplace, legal, and treatment settings. We evaluated two drug normalization procedures based on specific gravity and creatinine. These corrections were applied to urine specimens collected from three distinct groups (pain patients, heroin users, and marijuana/ cocaine users). Each group was unique in characteristics, study design, and dosing conditions. The results of the two normalization procedures were highly correlated (r=0.94; range, 0.78-0.99). Increases in percent positives by specific gravity and creatinine normalization were small (0.3% and -1.0%, respectively) for heroin users (normally hydrated subjects), modest (4.2-9.8%) for pain patients (unknown hydration state), and substantial (2- to 38-fold increases) for marijuana/cocaine users (excessively hydrated subjects). Despite some limitations, these normalization procedures provide alternative means of dealing with highly dilute, dilute, and concentrated urine specimens. Drug/metabolite concentration normalization by these procedures is recommended for urine testing programs, especially as a means of coping with dilute specimens.
authors.affiliation: Johns Hopkins School of Medicine, Department of Psychiatry and Behavioral Sciences, Baltimore, Maryland 21224, USA. Edward.cone@comcast.net
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Cone
authors.forename: Yale H
authors.initials: YH
authors.lastname: Caplan
authors.forename: Frank
authors.initials: F
authors.lastname: Moser
authors.forename: Tim
authors.initials: T
authors.lastname: Robert
authors.forename: Melinda K
authors.initials: MK
authors.lastname: Shelby
authors.forename: David L
authors.initials: DL
authors.lastname: Black
mesh_terms: D019970:Cocaine-Related Disorders / Q000175:diagnosis / Q000652:urine; D003404:Creatinine / Q000737:chemistry / Q000652:urine*; D003937:Diagnosis, Differential; D006556:Heroin Dependence / Q000175:diagnosis / Q000652:urine; D006801:Humans; D013287:Illicit Drugs / Q000737:chemistry / Q000652:urine*; D002189:Marijuana Abuse / Q000175:diagnosis / Q000652:urine; D008385:Marijuana Smoking / Q000652:urine; D010146:Pain / Q000188:drug therapy / Q000652:urine; D015203:Reproducibility of Results; D013046:Specific Gravity; D015813:Substance Abuse Detection / Q000379:methods*
chemical_list: D013287:Illicit Drugs; D003404:Creatinine