What is a Urine Drug Test Kit

What is a Urine Drug Test Kit?

Learn more about a urine drug test kit.

What is a urine drug test, and why are they necessary? Most rapid urine drug test kits produce a result in just a few minutes. Manufacturers describe them as a ‘competitive immunoassay’ in which various drugs of abuse compete for antibody binding sites with the conjugate on the analysis strips.

Urine drug test kits screen for drugs using what is considered “Dry chemistry” The chemicals necessary to detect the presence of drugs are dried into the antibody pads on the analysis strips. See the images below.

What is a Urine Drug Test Kit
Figure 1. is an analysis strip taken from inside of a urine test kit. Notice the letters ‘THC’? ; This indicates the analysis strip detects Marijuana.

How to interpret a POSITIVE result.

When the concentration of a drug is at or above the cut-off screen level, a drug is present. (figure 2.); This means the target drug present takes the antibody binding sites in the urine specimen. As a result, there will be no antibodies left to bond with the conjugate drug-protein on the analysis strip, and so no line will form for that drug.

What is a Urine Drug Test Kit
Figure 2.

How to interpret a NEGATIVE result.

When the concentration of a drug is below the cut-off screen level, no drug is present. (figure 3.) The unbound antibodies (which are bound to colloidal gold dye) will bind to the conjugate drug-protein on the analysis strip in a colorimetric reaction creating a visible line called the TEST LINE. The presence of any colored line, no matter how faint, indicates a negative result for that drug.

What is a Urine Drug Test Kit
Figure 3.

What are the principles of a urine drug test kit?

Urine drug test devices are based on the principle of competitive reaction between a drug or drug metabolites which may be present in a donor’s sample. The sample during the test migrates upward through capillary action and hydrates the analysis strip. When a drug is absent in the sample, the colored antibody will bind specifically to form a visible line in the test region.

When a drug is present in a person’s urine sample, the urine along with any drug metabolites migrate along the analysis strip. The metabolites will react and produce a chemical reaction, the result is no line on the test region will be present showing a positive result.

When a sufficient concentration of the drug is present in the sample, it will fill the limited antibody binding sites and prevent attachment of the colored antibody to the drug-protein on the test region: This is what makes the apparent colored line appear or disappear on the testing device. Therefore, the presence of the line on the test region (T) indicates a negative result for that drug, and the absence of the test line on the test region indicates a positive outcome.

A visible line is also generated by a different antigen or antibody reaction in the control region (C) of the analysis strip. This line should always appear, regardless of the presence of drugs or metabolites in the urine sample.

A negative urine sample will produce both the test line (T) and the control line (C). A positive urine sample will generate only a control line (C); the (C) line demonstrates that the test was successful.

What are the limitations of a urine drug test kit?

  • The drug test assay is designed for use with human urine only.
  • A positive result with any test only indicates the presence of a drug/metabolite and does not indicate or measure intoxication.
  • There is always a possibility that a procedural error or adulteration may interfere with the test and cause false results.
  • If adulteration is suspected, the test should be repeated with a new sample.

What if I am not able to test a urine sample immediately?

  • A specimen may be refrigerated at 2-8°C for up to 2 days or frozen at -20°C for a longer period of time.
  • Allow the urine specimen to reach room temperature before testing.
  • Allow the urine specimen previously frozen to reach room temperature before testing.
  • Handling of urine specimens and all materials should be disposed of as if capable of transmitting infection.
  • Gloves should be worn to avoid contact with skin.

What precautions should I be aware of when using a urine drug test?

  • Urine specimens may be potentially infectious.
  • Proper handling and disposal should be established prior to testing.
  • Always use a clean fresh container to avoid cross-contamination of urine samples.
  • Do not remove the device seal until you are ready to perform the analysis.
  • Do not use the expiration date.
  • A positive result does not always mean the donor has abused drugs as it may have been prescribed by a doctor.
  • Do not store and or expose test kits to temperatures greater than 30°C.
  • Do not freeze the testing device.

How do I interpret a urine drug analysis?

  • The drug test is used to obtain a visual, qualitative result and is intended for screening only.
  • The urine analysis assay provides only a preliminary result.
  • Allow the urine specimen, and or drug test kit to reach room temperature before testing.
  • Clinical consideration and professional judgment must be applied to any drug test result, particularly in evaluating a presumptive positive result (non-negative).
  • In order to obtain a confirmed result or confirmation, the urine sample should be sent for further analysis to a laboratory. Gas Chromatography/Mass Spectroscopy (GC/MS) is the preferred confirmation method.

Here is an example of three possible result scenarios:

What is a Urine Drug Test Kit

Colored lines appear in both Control Region (C) and Test Region (T). The line in the control region is the control line, which is used to indicate the test was successful. The line in the test region is the drug result line. The test line may have varying intensity either weaker or stronger in color than that of the control line: This is not an indication of drugs being present. A negative result for a drug indicates that the concentration of that drug in urine is below the cutoff level.

How do I know I tested successfully?

  • Manufactures include a built-in procedural control line for each test device. This line will form in the Control band region regardless of the presence or absence of drugs or metabolites.
  • The presence of the line in the Control region (C) indicates that the proper sample volume was collected and that the reagents migrated adequately.
  • If the line in the Control region (C) does not form, the test is considered invalid.
  • It is essential to make sure that the control values are within established limits; i.e.,  control lines are present otherwise the test results are invalid.
  • Send suspect samples to a SAMHSA approved laboratory for confirmation.

What is adulteration?

Adulteration is the tampering of a urine sample with the intention of altering the drug test result. Adulteration can cause false negatives by destroying the drug present in the urine. Dilution of urine is probably the most common adulteration method. One of the best ways to check for these is to use a Specimen or Adulterant test.

Bleach, vinegar, Visine, sodium bicarbonate, sodium nitrite, Drano, soft drinks, and hydrogen peroxide are examples used to cause adulteration. It is vital to ensure that integrity is intact before completing a drug test.

What is a Specimen Validity or Adulterant Check?

Manufacturers base their tests on the color response of chemical indicators that highlight possible adulterants. An administrator would check a urine sample to determine its integrity before testing.

specimen validity test chart
  • OX – Oxidant tests for the presence of Hydrogen Peroxide and Bleach which are oxidizing agents not found in urine.
  • SG – Specific gravity below 1.003 or above 1.030 is considered abnormal, which may indicate contamination.
  • pH- The standard urine pH ranges from 4 to 9. Urine pH below four or above 9 indicates contamination of the specimen with acids or alkalines.
  • GLU – Glutaraldehyde tests for the presence of aldehyde found in products purchased on the internet. Examples are ‘UrinAde’, ‘Your-In-Luck’, and ‘Clear Choice’. Glutaraldehyde is not found in urine.
  • NIT – Nitrites react to form a pink-red color complex. Urine samples containing nitrate at levels higher than 0.02 mg/dL are considered contaminated.
  • CRE – Creatinine reacts with a creatinine indicator to form a purplish-brown color complex. The color intensity is directly proportional to the concentration of creatinine, which is a waste by-product produced by the body. Urine samples with creatinine concentrations of less than 20 mg/mL are dilute, which may be an indication of contamination.

Adulterated samples will produce abnormal colors, and unadulterated urine will produce standard colors.

○ Additional Documents for testing.

Product information on Drug Adulteration Check Strips.

You may find it useful to read our instructions on how to use a urine drug test kit.

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