Frequently Asked Questions

Find answers to frequently asked questions below or browse our related articles on how to use the PharmChek® Sweat Patch, its many benefits, and much more.

Is it possible to have a positive sweat patch result and a negative urine test?

Yes. The sweat patch is a storage device and represents a much longer detection window than does testing for drugs using urine. In addition, urine tests are subject to various forms of adulteration including, but not limited to hydration, substitution, and physical adulteration using products designed to affect the testing procedures. Finally, a negative test result does not necessarily mean that no drugs were present. It simply means the drug in question was not detected above the cutoff level.

Will “passive” or inadvertent environmental exposure to a drug cause a positive test result?

The absorbent pad within the patch is protected from the environment by a layer of film composed of polyurethane coated with adhesive. The polyurethane film is a “semi-permeable membrane,” which allows the transfer of water vapor and gases while preventing outside contaminants from entering. In real-world conditions, there is no evidence that the membrane can be compromised.

Furthermore, to report a positive for cocaine or methamphetamine, the parent drug must be at or above the cutoff level AND the respective metabolite MUST be present at or above the LOQ (limit of quantitation). This reporting requirement minimizes the possibility of environmental contamination. The only way the drug metabolite is produced in the system is by actual ingestion (use) of the parent drug.

Can a positive result be from residual usage prior to the wear period?

With a positive patch result, it is not possible to determine exactly when the drug use took place, only that the drug use took place 24-48 hours before the application of the patch, during the wearing of the patch, or both.

It is possible to detect residual usage between multiple patch wear periods if drugs were consumed late in the first wear period and thus picked up early in the second patch wear period.

Is it possible to be allergic to the PharmChek Sweat Patch?

Allergic reactions do happen, but they are extremely rare. 3M, the maker of Tegaderm used in the manufacturing of the Sweat Patch states that less than 1% of the population is allergic to Tegaderm.

Furthermore, any individual truly allergic to Tegaderm is allergic to the surgical adhesive, not the film, and would be allergic to ALL surgical adhesives. This includes Band-Aids.

Tegaderm is a hypoallergenic material used as a wound dressing to cover catheter and IV sites of individuals in hospitals, and widely used within the medical field.

What is the window of detection?

The PharmChek® patch is a collection device designed to retain evidence of drug use for an extended period. It can detect use 24-48 hours before the application of the patch, during the wearing of the patch, or both.

For example: a PharmChek® patch worn for 7 days might be positive because of drug use on Day 1 or on Day 6.

Is the laboratory process subject to false-positive error?

False positives only apply to the immunoassay screen, not LC-MS/MS confirmation. All presumptive positive screens are sent for confirmation testing. As an additional safeguard, the laboratory utilizes blind quality assurance samples in the testing process.

All positive samples are placed in frozen storage for 12 months prior to disposal in the event a result is challenged.

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