Specimen Tampering & Verification
The attempt to adulterate a urine drug test sample generally falls into three categories:
- Urine substitution
- Ingestion of fluids or compounds for flushing out the system, diluting the sample, or interfering with the testing process
- Direct addition of adulterants to the urine specimen itself.
The most common form of adulteration is to substitute one’s urine with a clean urine. The best defense is to measure sample temperature, as urine specimens even held close to the body for extended periods of time will not produce a physiologically temperature-correct specimen.
Drinking large volumes of liquid, especially cranberry juice or vinegar is common practice as many of the drugs being tested are pH dependent. When large volumes of cranberry juice or vinegar are consumed, the urine pH is lowered, and the excretion rate of these drugs may increase. If timed correctly, large amounts of a drug may appear sooner in the sample.
One potentially effective method which may negatively impact the testing process is to consume large volumes of water, as short term water loading can increase urine volume up to eight fold. Therefore, if the individual’s drug concentration is near the cutoff of an assay, the urine may be diluted enough so that the sample will test below the cutoff level. Other attempted methods of adulteration include ingesting large amounts of vitamin C, vitamin B, niacin, Golden Seal, etc. All of these practices are ineffective.
Adulteration of a urine sample with various chemicals may inactivate some of the laboratory testing methodologies, most notably, the enzyme immunoassay’s. Addition of compounds such as sodium chloride, sodium bicarbonate, hydrogen peroxide, bleach, alcohols, blood, various soaps, etc. are shown to produce both false negatives and false positives.
The current list of urine adulterants is ever changing as the Internet provides an informational source, as well as a retail outlet for commercial products capable of affecting the outcome of some urine drug testing methodologies.
How to detect adulteration
Specimen Temperature – The most effective means to detect specimen dilution, adulteration, or substitution is to measure the sample’s temperature. The collector should measure the temperature utilizing the temperature strip affixed to the specimen container within four minutes of collection; it should read between 90 and 100 degrees Fahrenheit. The urine temperature should be noted on the requisition form.
Urine Appearance and Odor – Adulterants such as isopropyl alcohol, soaps, bleach and perfumes are readily identified by their odor. Soaps are also identified by excessive bubbling. Use of solid adulterants is detected by the presence of residues in the container.
Creatinine – Creatinine is a waste product produced by the body and excreted in the urine. Our laboratory has the capability of determining a quantitative level of creatinine in a urine sample. A normal urine sample has a creatinine level greater than or equal to 20 mg/dL. If no creatinine is present, the sample submitted is not urine. Common substitutes for urine are apple juice and tea. Urine specimens with creatinine levels between 2 and 10 mg/dL are usually a result of ingestion of large volumes of water (or other liquid), termed short term water loading. This is a very common practice when attempting to dilute a urine so that any drugs in the urine will be diluted below analytical testing cutoff levels. Urine creatinine levels below 2.0 mg/dL indicate the specimen is not consistent with human urine.
Specific Gravity – Specific gravity is an indication of the amount of solid particles dissolved in a urine sample. We can determine a quantitative level of specific gravity in a urine sample. A normal urine sample has a specific gravity of greater than or equal to 1.003. If a urine sample has a creatinine value less than 20 mg/dL and a specific gravity less than 1.003, then the sample is considered diluted and will be reported as such. This dilution can come from either drinking large volumes of liquid before providing a urine sample, or pouring something into the urine cup at the time of collection. Either way, the sample is considered diluted, and may not provide a proper evaluation of drug use by the donor/patient. We advise re-testing if a sample appears to have been diluted.
pH – A pH test determines the degree of acidity or alkalinity of a urine sample. A normal urine specimen has a pH between 5 and 8. Our acceptable pH range runs from 3.0 to 10.9. This expanded range allows for medical conditions and other factors (such as bacterial activity) which may alter the pH of a urine sample without any malicious intent on the part of the donor. Any sample with an abnormal pH outside of our range of 3.0 to 10.9 is an adulterated sample, meaning something has been added to the urine sample after voiding for the purpose of tampering with the drug testing process. Bleach and ammonia, for example, will produce a basic pH (11 or greater). Lemon juice and vinegar can produce an acidic pH (3 or lower). Specimens with pH values less than 3 or greater than or equal to 11 will be reported as adulterated. A specimen reported as adulterated should be interpreted with the same severity as a positive drug test result.
Oxidant testing – While it is impossible to test for all possible adulterants, most fall into the category of oxidizing agents. A general oxidant screen test is designed to identify specimens tampered with oxidizing agents. Specimens positive by this methodology will be reported as “Invalid: possible oxidant activity”.