A 0.63 Blood-to-Plasma Ratio Was an Assumption in the Inhaled-THC Model
The inhaled-THC modeling study used a blood-to-plasma ratio of 0.63 to relate whole-blood measurements to plasma-based pharmacokinetic work. It did not measure that ratio separately in every participant.
The original specimens were whole blood
Researchers quantified THC in whole blood. For model comparison and fitting, they applied an external ratio to connect those values with the plasma framework used in earlier studies. The transformed concentration therefore depended on both a laboratory measurement and a matrix assumption.
Conversion does not create a paired plasma specimen
A calculated plasma-equivalent value should not be labeled directly assayed plasma THC. The ratio’s use in one modeling exercise also does not establish that it is constant across all individuals, collection intervals or analytical settings. The current data did not independently test every such application.
Keep the matrix in the scientific conclusion
The model’s estimated doses and parameters should be interpreted with that conversion in view. Quoting a numerical concentration without specifying whether it was measured or transformed loses information relevant to uncertainty. Neither a whole-blood result nor its calculated plasma counterpart supplies a functional impairment finding. For a disputed comparison, identify the original specimen and the conversion basis before treating two reported numbers as directly comparable observations.
Related analysis: the study’s broader findings and limitations.
