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Creatinine analysis in single collection urine specimens
S B Needleman1, M Porvaznik, D Ander
1Navy Drug Screening Laboratory, Great Lakes, IL.
Journal of Forensic Sciences
|July 1, 1992
Summary
Urine creatinine concentration decreases with fluid intake, indicating specimen dilution. Low creatinine levels (≤ 30 mg/dL) suggest potential tampering, aiding drug use detection efforts.
Area of Science:
- Clinical Chemistry
- Toxicology
- Forensic Science
Background:
- Urine adulteration is a concern in drug testing.
- Creatinine levels in urine can be affected by fluid intake.
- Accurate interpretation of urine drug tests requires specimen integrity.
Purpose of the Study:
- To investigate the relationship between fluid intake and urine creatinine concentration.
- To determine the time course of creatinine decline after fluid ingestion.
- To establish creatinine concentration thresholds for identifying potential urine specimen adulteration.
Main Methods:
- Controlled and uncontrolled fluid intake studies with volunteers.
- Collection of urine specimens at various time points.
- Creatinine analysis using a modified Abbott TDx procedure.
Main Results:
- Single urine specimen creatinine values correlate with 24-hour pooled samples.
- Creatinine concentration decreases significantly within 4-7 hours of fluid intake.
- Creatinine levels of ≤ 30 mg/dL are used as a cutoff for potential adulteration, with ≤ 10 mg/dL suggesting water replacement.
Conclusions:
- Urine creatinine concentration is a sensitive indicator of dilution due to fluid intake.
- Low creatinine levels can signify urine specimen adulteration, aiding in the detection of drug use avoidance.
- Established cutoffs help differentiate between dilute specimens and those tampered with.