The method reported patch recovery of 44–46%, while blind quality-control patches were quantified acceptably. Physical extraction recovery and final concentration accuracy were different performance measurements.
The paper reported both outputs
For the oral-dosing workflow, recovery from patches was 44–46%, with a quantification limit of 0.4 ng THC per patch. Separately, blind low-, medium- and high-level patches were sent with study specimens to assess the other testing workflow. Their measured results were within 20% of targets.
These checks described laboratory performance under specified conditions. They were not measurements of the fraction of an administered THC dose excreted into sweat.
Recovery is not a universal correction factor
A reported extraction loss does not justify multiplying every clinical result by the inverse recovery. Calibration, internal-standard treatment and method validation affect the final reported quantity. Conversely, acceptable quality-control accuracy does not establish complete extraction from every authentic patch.
Retain the question being answered
The study supports evaluating preparation and quantification separately. It does not provide an exact total-body excreted amount, a patch-to-blood conversion or a consumed-dose calculator. For an individual result, use the laboratory’s own validated method and the patch wear history rather than transferring a single recovery percentage from this experiment.
Related reading: cannabinoid assay validation.
Research cited
Huestis and colleagues (2007). Excretion of Δ9-Tetrahydrocannabinol in Sweat. DOI: 10.1016/j.forsciint.2007.04.002.
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