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Improving the Pharmcheck(TM) Sweat Patch: Reducing False Positives From Environmental Contamination and Increasing Drug Detection, Final Report

NCJ Number
Melissa Long; David A. Kidwell
Date Published
September 2002
44 pages
This report examines the reliability of the Pharmcheck(TM) sweat patch used in detecting drug use by exploring the external contamination from within (CFWI) or under the sweat collection patch, testing the different methods of removing drugs from contaminated skin, testing if the criteria for the last cleaning swab was sufficient in detecting prior contamination, and comparing various patch designs for their effectiveness in absorbing and retaining drugs on the skin.
Ingested drugs have been known to appear in sweat. This has created the development of sweat collection devices for use in drug detection, such as the Pharmcheck(TM) sweat patch. However, externally applied drugs or drugs deposited on the skin, can cause false positives or contamination from within (CFWI). Different cleaning procedures are used to remove externally applied drugs, however some drugs can remain causing false positives, and if an individual lives in a drug-contaminated environment, CFWI could occur also producing misleading results for drug use. This final report attempts to examine the degree of CFWI, the various methods utilized in removing drugs from contaminated skin, examines whether the 10 percent criteria for the last cleaning swab is sufficient to detect prior contamination, and lastly, compares the patch designs to determine their effectiveness in absorbing and retaining drugs on the skin. Results indicated that the current method of cleaning the skin prior to patch application would never be 100 percent effective in removing all drugs present from environmental contamination. To provide a margin of error, future experiments should be performed with greatly increased amounts of drugs applied to skin. In addition, experiments testing the patch should be re-evaluated due to prior skin contamination not being examined. Criteria outlined and suggested include a stronger anionic exchange group on the surface of the absorptive pad that should allow the drugs to bind and accumulate them in the patch better and adding glycerol to the patch to help transfer drugs by providing a better transfer medium and eliminating the dependence on active sweating. It was suggested that saving the wipes after cleaning the skin and testing them would likely detect CFWI, thereby supporting a positive result. A combination of better skin procedures with saving the cleaning materials for additional analysis could allow the patch to be used under almost any contamination scenario. Figures, tables and references