THC-Glucuronide Stability Evidence Was Stronger in Plasma Than Blood
The study reported THC-glucuronide stability in plasma, while very few blood specimens had quantifiable concentrations. The two matrices did not provide equally informative evidence for that analyte.
The plasma observation
High plasma THC-glucuronide pools showed no significant group change over the tested periods: one week at room temperature, twenty-six weeks refrigerated and fifty-two weeks frozen. The report also noted an individual decrease after room-temperature storage. A stable group result does not require identical behavior in every person’s specimen.
The blood comparison had a different limitation
Blood THC-glucuronide exceeded the quantification limit in only two participants, which the authors said confounded statistical interpretation. That limited dataset should not be translated into a confident claim that blood and plasma have the same stability, or that one matrix is definitively unstable whenever the other is stable.
What to retain in a case review
Identify whether the reported analyte is THC-glucuronide or THC-COOH-glucuronide; they are different conjugates. Then match the specimen and handling conditions to the supporting data. The work concerns stored authentic human samples after smoking, not a validated matrix conversion factor, a precise last-use clock or an impairment threshold. Sparse measurements and group-level null findings need their own qualifications.
Related analysis: free metabolite changes during specimen storage.
Research cited
Scheidweiler and colleagues (2013). In Vitro Stability of Free and Glucuronidated Cannabinoids in Blood and Plasma Following Controlled Smoked Cannabis. DOI: 10.1373/clinchem.2012.201467.
