Creatinine Analysis in Single Collection Urine Specimens

Abstract

Controlled and uncontrolled fluid intake studies were conducted on series of volunteers over the 6 or 12 h of the study periods. Urine specimens were obtained from each subject randomly or at specified times relative to fluid ingestion. Creatinine analysis performed by a modification of the Abbott TDx procedure demonstrates that the values obtained from single collection specimens fall almost in the same range as the values from 24 h pooled collection specimens. The creatinine concentration can be used to indicate possible adulteration of urine specimens by dilution as a means of avoiding detection of use of drugs of abuse. Between 4 and 7 h are required for a decrease in creatinine concentration to about 100 mg/dL from an initial mean of about 170 mg/dL. A minimum of 6 h is needed for any creatinine value to fall to 50 mg/dL or less. Thus, it appears that creatinine output is sensitive to the amount of fluid ingested, but the relationship is neither linear nor immediate. The absence of a significant creatinine concentration in a specimen can be used as an indication of direct or indirect adulteration of the urine specimen by dilution or replacement with water. At NDSL-Great Lakes, a decline of the creatinine concentration to 30 mg/dL is used as a cutoff for differentiating between urine specimens that might have been tampered with to avoid detection of drug use and those specimens that are dilute for other reasons. Values at 10 mg/dL or less are suggestive of replacement by water. The information is provided to local commands for investigation prior to initiation of punitive action by the command.

Urine-creatinine concentration as a marker of urine dilution: Reflections using a cohort of 45,000 samples

“…However, the 2.5% percentile of the urine-creatinine concentration for women (189 mg/L) was clearly below suggested cut-off levels of <300 mg/L [2], of <250 mg/L [3] and of <200 mg/L [4,5] and the same is true for men (256 mg/L 2.5% percentile) when using cutoffs of >250 mg/L. This situation is not acceptable since it bears the risk of a high rate of false classifications between physiological and adulterated urine samples.…”

“…The latter could clearly be attributed to a very slender habitus of the women tested. The consequences would have been: 18 false-positives (26% out of 70 measurements) when applying a cut-off of <300 mg/L according to [2], 13 false-positives (19%) when using a cut-off of <200 mg/L like given in [4,5] and still 2 false-positives (3%) with a cut-off of <100 mg/L. The latter (3%) are still a relatively high rate of false-positives from the forensic point of view.…”

“…Cut-off values of e.g. 300 mg/L [2], 250 mg/L [3], 200 mg/L [4,5] and 50 mg/L [6] have been suggested. Current German regulations for re-issuing drivers licences rate urinecreatinine concentrations of <100 mg/L as ''water'', of <200 mg/L as ''not useable'' and already concentrations of <900-1000 mg/L as ''suspicious of urine adulteration'' [7].…”

Quantification of a Methadone Metabolite (EDDP) in Urine: Assessment of Compliance

“…28 Most of these applications, however, have been designed with the specific aim of avoiding false negative results in drug screening programs due to very dilute urine specimens. 22,29,30 Few, however, have attempted to employ creatinine adjustments in the clinical setting. Manno et al 23 reported that the Syva EMIT-d.a.u.…”

False Negative Results in Testing for Drugs of Abuse from Diluted Urine

“…Dilution of urine either by drinking excessive amounts of water ("internal dilution") or by adding water to a urine sample ("external dilution") or by taking diuretics or other special teas is a serious problem in drugs of abuse (DOA) testing [1][2][3][4][5]. Many subjects use this tampering method in order to dilute drugs in urine to levels that are below cutoff values in order to obtain false negative results [6].…”