Detection of Fake or Adulterate Urine Sample
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Detection of a fake or adulterated urine sample is necessary before going to the further process of urine testing in the laboratory. Urine adulteration causes false-positive and false-negative results. However, most attempts of a fake or adulteration in a urine sample can be detected either by a trained collection site personnel or by a laboratory technician during the testing process. Coordination and cooperation between the collection site and the testing laboratory provide effective and reliable test results. There are some methods by which fake or adulterated urine can easily identify.
1. Specimen Temperature
If the specimen collection is not witnessed, the most common method to detect the fake specimen or diluted specimen is to measure the temperature of the sample. The temperature is measured within 3-4 minutes of collection. The temperature of the specimen should be in between 90° and 100° Fahrenheit.
2. pH of Specimen
The pH of human urine is between 4.0 and 9.0. If the pH of the specimen is outside of this range is an indication that the specimen may have been manipulated.
3. Specific Gravity
This is also called as relative mass density. It depends on the number of solutes in a solution. It is basically a comparison of the density of urine against the density of distilled water at a particular temperature. It describes the normal levels of dilution present in the sample. The specific gravity of human urine is between 1.003 and 1.035*. If the specific gravity of the specimen is outside of this range then it is possible that the sample was artificially diluted by an adulterant. Also, note that the specific gravity of pure water at 4° Celsius is 1.000.
4. Appearance and Odor
Freshly voided urine has a typical aromatic odor due to volatile organic acids. After standing, urine develops ammoniacal odor (formation of ammonia occurs when urea is decomposed by bacteria). Some abnormal odors with associated conditions are:
- Fruity: Ketoacidosis, starvation
- Mousy or musty: Phenylketonuria
- Fishy: Urinary tract infection with Proteus, tyrosinemia.
- Ammoniacal: Urinary tract infection with Escherichia coli, old standing urine.
- Foul: Urinary tract infection
- Sulfurous: Cystinuria.
Adulterants such as soaps, perfumes, and isopropyl alcohol are readily identified by their odor. Use of solid adulterants is detected by the presence of residues in the container. Soaps are also identified by excessive bubbling.
5. Testing for PCC/Oxidants
Testing for PCC/Oxidants can detect the residues of bleach or peroxide in the specimen, and since normal urine should not contain any traces of oxidants. Finding of these traces typically is an indication that the specimen may have been adulterated.
6. Glutaraldehyde (C5H8O2)
Glutaraldehyde is a toxic chemical which is used as a disinfectant to sterile heat-sensitive surgical, dental and medical equipment. It is a known adulterant that causes false negative results by tampering with the naturally occurring enzymes in urine. This adulterant is not commonly present in human urine, and since detection of glutaraldehyde is an indication that the specimen is adulterated.
Creatinine is a metabolic byproduct of the body muscle tissues, and normally present in urine. Therefore urine creatinine test can be used as a marker to specifically identify a specimen as urine. Normally, creatinine level of a random urine sample is more than 20 mg/dL, while specimen with creatinine level between 10 and 20 mg/dL is an indication of increased water consumption or liquid ingestion. A urine specimen with creatinine level between 2 and 10 mg/dL is an indication of the large volume of water or other liquid ingestion and termed as short-term water loading. This is a very common practice to bypass drug test by diluting urine. A urine sample with creatinine level below 2.0 mg/dL is not accepted and indicate that the sample is not consistent with human urine.