Common Types of Drug Tests

There are many ways to detect the presence of drugs in the body. They are

  • Urine Drug Tests
  • Hair Drug Tests
  • Blood Drug Tests
  • Saliva Drug Tests

Urine drug testing is the most common because it is relatively inexpensive compared to the other tests. Hair drug testing in particular is very expensive. It is also relatively easy to collect a sample for urine drug testing, as opposed to taking a blood sample for a blood drug test. This would probably increase resistance to drug testing exponentially. So we will deal with urine drug tests in these pages.

There are several types of urine drug tests commonly used to detect the presence of drugs. Most can detect several types of drugs, but they vary in detection accuracy.

Drug tests deal in a high level of precision. Drug test results are expressed in nanograms per milliliter. A nanogram means one billionth of gram, or 0.000000001 grams, usually described as parts per billion (PPB). The level between a positive and negative drug test result varies according to the type of drug, but it can be as little as one part per billion. For example, if the level for a positive cocaine drug test is 50 PPB, then a level of 49 PPB would be considered a negative cocaine drug test result. So the difference between landing the great job or being turned away is quite miniscule.

The most common types of urine drug testing used to detect drugs are described below.

There are some basic field drug tests where a few drops of urine are placed on a sheet of paper treated with certain chemicals. Drugs are detected if the paper changes color. These drug tests are inexpensive and require little training to conduct. While they detect presence, they do not give specific results for specific drugs. Other drug tests provide more specific results.

Thin layer chromatography (TLC) is a urine drug test that can detect about 40 different drugs. For this test a few drops of urine are added to a gel substance and placed on a microscope slide. Then, the edge of the slide is dipped in a chemical, and the gel draws the chemical across the slide. The various drug residues in the urine migrate through the chemical at different rates, causing them to separate and appear as different colored dots scattered around the slide. A lab technician examines the slide under a microscope, looking for colored dots that indicate the presence of various drugs. While the size of the colored dots may indicate the amount of the drug present, TLC is typically used as a preliminary screening drug test. A positive result usually means the urine will be drug tested with a more advanced method. The absence of these colored dots means there are no drugs present in the system.

Enzyme immunoassay (EIA) uses a machine to test for the presence of 10 different drugs in urine. The machine has 10 channels - each channel tests for a different drug type. A small urine sample is placed in each channel, and each channel has two chemicals added to it. The first chemical reacts with the drug, and this reaction causes the second chemical to change color. If no drugs are present, then the first reaction does not take place, therefore the second chemical does not cause the color change.

After the chemicals are added, the samples for each channel are photographed then examined by a technician. The intensity of the color in each channel indicates the amount of the drug present. EIA is a common screening drug test method. If a positive result occurs a more accurate drug test is conducted.

Radioimmunossay (RIA) is similar to EIA. It also uses a machine with 10 channels, but it employs radiation in combination with chemicals for drug detection. Like EIA, a small sample of urine is placed in each channel. A radioactive chemical is added to each channel, and this chemical sticks to drug molecules. The presence of radioactivy in a particular channel indicates the presence of a particular drug. If a channel does show radioactively, then that particular drug is not present in the urine. RAI is also typically used as a screening drug test.

One of the most accurate drug testing methods is gas chromatography/mass spectrometry (GC/MS), plus it can test for virtually any drug. This drug test requires an expensive machine that is commonly used for forensic testing as well. The machine coverts the urine into a gas, and then sends it down a long tube. Different types of molecules travel at different speeds through the tube, and arrive at the mass spectrometry stage separately. Now individual molecules can be analyzed using a charge versus mass analysis, and the presence of all the individual components of the urine are identified, including drugs.

Since GC/MS is an expensive drug test to conduct, many organizations and labs use a less expensive test as a screening drug test first, then use GC/MS on the urine sample if it tests positive with one of the screening tests. This is important, because to pass a drug test you usually need to only pass the less reliable screening drug test. If you pass the screening drug test, a GC/MS test is not conducted.

Even more importantly in terms of privacy, these drug tests may indicate whether a drug is present in your urine, but these drug tests can not indicate when the drug was taken, or if an employee was under the influence of drugs while on the job. Should employers be able to control employee activities when they are not at work? If an employee shows up and does their job at an acceptable level, what they do on their own time should be their own business. That is the inherent unfairness of drug testing, as well as a violation of privacy rights.