How the patch works
A sweat patch is an adhesive patch applied to the skin, typically the upper arm or back, by a TrueTest collector. It is worn continuously and collects drugs excreted in sweat for the whole time it is on. At the end of the wear period the collector removes it, seals it under chain of custody, and applies a fresh one if the program continues. This is the advantage of sweat patch testing: continual monitoring.
The protocol is a seven-day wear on a set weekday. The patch may be worn up to ten days; the extra days exist to cover a day the donor cannot come in, not to stretch the schedule. Patches worn habitually past seven days begin to lift, and a patch that is lost is a wear period that is lost.
The standard panel is amphetamine, methamphetamine, cocaine, PCP, opiates, and THC. It can be expanded to additional opiates and fentanyl. The patch does not detect alcohol.
The patch is tamper-evident. Removal or interference cannot be prevented, but it can be detected.
TrueTest collectors are trained on the manufacturer’s application and removal procedure, and every patch is applied and removed by a TrueTest collector, never by the donor.
Reading the report
Every patch is analyzed by Clinical Reference Laboratory in Lenexa, Kansas — the only laboratory authorized to test it, a nationally recognized forensic toxicology laboratory, and SAMHSA-certified. The report has two parts.
Initial test. One line per drug, each reported negative or positive against a screening cutoff.
Confirmation. Any drug that screened positive is confirmed by mass spectrometry and reported as a number in ng/mL against a confirmation cutoff. Where the drug has a metabolite, the metabolite is reported on its own line.
The quantitative number is what the patch collected over the entire wear period. It is cumulative. The report shows the wear dates; TrueTest reports the number as the laboratory reported it and does not adjust it for wear days.
A positive result establishes that the drug was present during the wear period. It cannot say on which day, how much was used, or how often.
How a positive is determined
For drugs with a metabolite — cocaine and methamphetamine on the standard panel — the laboratory reports the parent drug and the metabolite separately, and the metabolite has a range below its cutoff, reported as PRESENT.
The rule the laboratory applies:
- Metabolite at or above its cutoff → positive, regardless of what the parent drug shows.
- Parent drug at or above its cutoff and metabolite in the PRESENT range → positive.
- Parent drug at or above its cutoff and metabolite below the PRESENT range → negative.
A patch that isn’t there at removal
A donor may tell us the patch fell off. TrueTest cannot determine whether a patch came off on its own or was removed. Every donor is told that if the patch appears to be lifting, take a picture and text it to us; from that we decide the next step. Patches do not come off all at once — lifting is visible before a patch is lost.
If the patch is not attached to the body when the donor arrives for removal, there is no result. The patch is cancelled, a notice goes out, and a new patch is applied at that visit.
Prescriptions
Normal MRO procedures apply to all sweat patch results.
What the order has to say
For a sweat patch program the order should set the duration of the program and the change schedule. A seven-day schedule on a fixed weekday is the protocol; an order that leaves the wear period open invites the ten-day stretch that loses patches and creates longer result reporting times.