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Normalization of urinary drug concentrations with specific gravity and creatinine.

Edward J Cone¹, Yale H Caplan, Frank Moser

¹Johns Hopkins School of Medicine, Department of Psychiatry and Behavioral Sciences, Baltimore, Maryland 21224, USA. Edward.cone@comcast.net

Journal of Analytical Toxicology

|January 24, 2009

Summary

This summary is machine-generated.

Urine drug test results can be falsely negative due to excessive fluid intake. Normalization methods using specific gravity and creatinine improve accuracy, especially for dilute samples in drug monitoring programs.

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Area of Science:

Forensic Toxicology
Analytical Chemistry
Clinical Chemistry

Background:

Dilute urine samples can lead to false-negative drug test results.
Current drug testing protocols do not routinely use normalization for hydration variations.
Normalization methods are used in anti-doping and environmental monitoring.

Purpose of the Study:

To evaluate two drug normalization procedures (specific gravity and creatinine) for urine specimens.
To assess the effectiveness of these normalization methods across different user groups and hydration states.

Main Methods:

Applied specific gravity and creatinine normalization to urine samples from pain patients, heroin users, and marijuana/cocaine users.
Compared the results of the two normalization methods.
Analyzed the impact of normalization on positive detection rates for each group.

Main Results:

The two normalization procedures showed high correlation (r=0.94).
Normalization led to small positive rate changes in normally hydrated subjects.
Substantial increases in positive detection rates were observed in excessively hydrated subjects (marijuana/cocaine users).

Conclusions:

Specific gravity and creatinine normalization are effective in correcting for hydration variations in urine drug testing.
These methods improve the detection of drugs/metabolites in dilute urine specimens.
Normalization is recommended for urine testing programs to mitigate issues with dilute samples.