The Substance Abuse and Mental Health Services Administration (SAMHSA) in conjunction with the U.S. Department of Transportation (DOT) identify certain problems that may be encountered with urine specimens submitted for drug testing. The testing laboratory should have procedures in place to identify compromised specimens and to handle them appropriately.
Terms for Specimen Problems:
(1) dilute: The specimen contains more water than normal. This may be
(1a) intentional (overhydration, addition of water), in order to reduce the concentration of a drug to a level below the analytical cutoff
(1b) unintentional
(2) substituted, where a specimen that does not exhibit the clinical signs or characteristics associated with normal human urine.
(3) adulterated, where the specimen is urine to which something has been added
(4) invalid (incongruent or inconsistent)
|
Urine Creatinine in mg/dL |
Specific Gravity |
Interpretation |
|
< 2 |
< 1.002 (<= 1.001) |
substituted |
|
< 2 |
>= 1.002 and < 1.020 |
inconsistent |
|
< 2 |
>= 1.020 |
substituted |
|
>= 2 |
1.000 |
inconsistent |
|
>= 2 and < 20 |
>= 1.020 |
inconsistent |
|
>=2 and < 20 |
> 1.000 and < 1.003 (1.001 or 1.002) |
dilute (provided not substituted or invalid) |
where:
• A donor with a urine specimen showing a creatinine >= 2 mg/dL and <= 5 mg/dL is subject to a immediate, directly observed collection.
|
pH |
Interpretation |
|
< 3 |
adulterated |
|
>= 3 to <4.5 |
invalid |
|
4.5 to 8.9 |
expected |
|
>= 9 to < 11.0 |
invalid |
|
>= 11.0 |
adulterated |
|
Urine Finding |
Adulterated |
Invalid |
|
pH |
< 3 or >= 11 |
3.0 to 4.4, 9.0 to 10.9 |
|
nitrite concentration |
>= 500 mg/L (500 µg/mL) |
200 - 499 mg/L (µg/mL) |
|
chromate |
positively identified (>= 50 µg/mL) |
possible |
|
halogen (bleach, iodine, fluoride) |
positively identified |
possible |
|
glutaraldehyde |
positively identified |
possible |
|
pyridine (pyridium chlorochromate) |
positively identified |
possible |
|
surfactant (detergent) |
positively identified |
possible |
|
an exogenous substance is present in the specimen |
positively identified |
possible and unidentified |
|
an endogenous substance |
present at a higher concentration than normal physiological levels |
|
|
chemical interference with GC/MS |
|
present |
|
other |
|
incongruent findings in urine creatinine or specific gravity (above) |
where:
• One test for specimen substitution is to look for IgG in the urine, which is a normal finding in human urine but not urine of other species.
• An exogenous substance is any substance which is not a normal constituent of urine. This includes substances intended to interfere with an analytical test.
• An endogenous substance is any substance which is a normal constituent of urine.
• A positive test for surfactant is >= 100 µg/mL dodecylbenzene sulfone equivalent.
• GC/MS is gas chromatography mass spectroscopy.
Specialty: Toxicology, Emergency Medicine, Critical Care
ICD-10: ,
