Eight Cannabinoid Analytes From a Tiny Blood Sample: What Microsampling Validation Shows
A microsampling method measured CBD, THC and multiple metabolites using approximately 30 microliters of blood. Its successful application to seven treated patients demonstrated analytical feasibility, not comparative efficacy of their CBD formulations or a new impairment test.
A broader panel than CBD alone
The researchers developed a liquid chromatography–tandem mass spectrometry assay with volumetric absorptive microsampling. The panel included CBD, four CBD metabolites, THC, 11-hydroxy-THC and THC-COOH.
The matrix was blood collected on a microsampling tip. The extraction and hydrolysis procedure forms part of the definition of the reported measurements. Results should not automatically be treated as interchangeable with plasma, serum or a method that measures only unconjugated analytes.
What was validated in the laboratory?
Validation assessed sensitivity, calibration, selectivity, precision, accuracy, carryover and stability. Quantification limits differed by analyte: 0.25 ng/mL for THC and its two included metabolites, 1.5 ng/mL for CBD and 7-hydroxy-CBD, and 3.5 ng/mL for 7-carboxy-CBD.
These limits explain why “not detected” and a measured low concentration require analyte-specific interpretation. They are analytical performance characteristics, rather than concentrations marking therapeutic success or functional impairment.
Seven patients provided a proof of concept
The clinical application involved seven patients aged three to twenty receiving different CBD preparations and regimens. CBD and its included metabolites were detected, with 7-carboxy-CBD generally the most abundant. THC, 11-hydroxy-THC and THC-COOH were not detected in these samples.
The nondetections are informative under the assay’s conditions. They do not prove that each formulation contained absolutely no THC, that no earlier exposure occurred, or that every CBD product would yield the same result.
Some patients using galenic oils had higher CBD concentrations than patients using other preparations. But these were different people receiving different regimens, not a randomized formulation comparison. The concentration differences cannot establish which product was intrinsically more bioavailable or more effective.
What a clinical or forensic user should request
Interpretation requires collection time, actual dose and units, product composition, sample type, handling conditions and the assay’s treatment of conjugates. A broad metabolite panel may improve description of exposure while still leaving the patient’s clinical response unresolved.
The practical strength of the work is a smaller-volume collection approach that may ease repeated sampling, particularly in children. The seven-patient demonstration does not establish concentration targets for seizure control, individual dose equivalence or readiness for safety-sensitive activity.
Related analysis: Adult Epilepsy CBD Outcomes: Treatment Retention and Confounding Matter.
Primary research
Federica Pigliasco and colleagues. Cannabidiol, ∆9-tetrahydrocannabinol, and metabolites in human blood by volumetric absorptive microsampling and LC-MS/MS following controlled administration in epilepsy patients. Frontiers in Pharmacology (2022). DOI: 10.3389/fphar.2022.1038754.
