Sweat Patch Procedures

The sweat patch is a gauze pad that is applied to the arm like a bandage and collects chemicals excreted through sweat, which is then sent to a lab for analysis. The procedures used to obtain accurate results from sweat patch tests include properly cleaning the arm and applying the patch, then the series of tests that determine what, if any, type of illegal substances are present on the patch.

About

• The sweat patch is a drug testing device that detects the presence of drugs in the system based on the process of perspiration. As the person wearing the patch sweats over the course of wearing the patch, the patch collects the chemicals excreted. This sample is then sent to a lab for analysis and drug detection. Sweat patches are composed of a small piece of gauze attached to a plastic protective membrane, with a small amount of adhesive around the perimeter. These patches are commonly used to detect the presence of drugs in the sweat of prison inmates and parolees.

Application

• Before the patch is applied to the skin, the upper arm is swabbed using isopropyl alcohol to clean and disinfect the area. The patch is then applied and worn for seven to 14 days. During this time it collects the chemicals excreted by the system during perspiration. After this period, the recipient of the test returns to the testing site to have the patch removed. The patch is then removed by peeling it off and is sent to a lab for analysis.

Analysis

• During analysis, technicians examine the patch using an immunoassay system also used for urinalysis drug tests. If the presence of any type of drug is discovered on the gauze pad, technicians then conduct further tests to determine the type of drug present. Gas chromatography and mass spectrometry screening are two types of procedures used to determine the particular drug excretion found on the gauze pad. Gas chromatography separates compounds found on the pad by vaporizing them, while mass spectrometry identifies the chemical compounds on the pad by determining the mass and chemical makeup of the atoms on the pad. These two procedures can identify most types of drugs excreted onto the pad.

Considerations

• There are many advantages and disadvantages to using sweat patches for drug testing. Because the subject wears the patch for one to two weeks, there is a longer window for testing than with standard urinalysis tests, which provides screeners with more opportunities to identify drug abuse and also helps to prevent drug abuse. The patch is also easy to apply and remove. However, according to scientific studies, the sweat patch can produce false positives when a drug residue on the skin attaches to the pad. Laboratory analysis cannot determine the difference between secreted drug compounds and compounds found on the skin. Additionally, improperly trained testing centers can compromise the results by applying and removing the patch incorrectly.