The AOPA article is simply wrong.
"But there is currently no direct test for THC levels in a person, like a blood test for alcohol. Therefore, the DOT test does not report the level of THC, but rather the level of cannabinoid metabolites, the chemicals in the blood left after the body has metabolized THC. As for CBD products, the body metabolizes CBD, which is also a cannabinoid, in the same way so it leaves the same metabolites."
While anything produced by
Cannabis sativa is termed an cannabinoid, this also refers to compounds that aren't closely related to the various THC compounds, so they can't have the same metabolites.
The initial test is the urine test- this is an antibody test for THC compounds as described in the citation above.
They can test for CBD - I'm not sure why the citation I thought I posted didn't show, but here it is now:
https://www.labcorp.com/tests/701907/cannabidiol-cbd-tetrahydrocannabinol-thc-ratio-urine
They can then test for CBD metabolites, and from the ratio of THC and CBD metabolites, determine if the person being tested was using CBD contaminated with THC, or was using a THC product
I was merely attempting to correct the false statement the CBD has the same metabolic markers as THC.
AFAIK, the FAA stops at the urine test if there is any THC found, so form a practical point of view, AOPA is correct. They see THC in the urine test and you fail, full stop.