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.

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.

Studies involving this concern were conducted by applying drugs to the exterior of the patch and subsequently collecting and analyzing the absorbent pad. No drugs were found in these experiments.

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 up to 24 hours prior to removal, 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 the sweat patch subject to contamination?

No, when following proper operating procedures in a real-world environment. Experiments have looked at scenarios such as wetting the absorbent pad with various solutions and buffers, varying the pH of the of the solution containing drugs that was applied to the exterior of the polyurethane membrane, and varying the temperature and time that the varying solutions are allowed to sit or incubate on the exterior of the polyurethane membrane.

These studies have demonstrated that when both the inside and the outside of the patch were dry, no drug transfer could be noted. Under certain conditions, the outer polyurethane membrane can be altered and made permeable to the diffusion of applied drugs onto the absorbent pad.

However, these conditions are not what one would realistically expect to encounter in real-world situations.

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 (up to 24 hours prior to removal), 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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