The concentrations obtained from such analyses can often be helpful in distinguishing active use from passive exposure, elapsed time since use, and extent or duration of use.
Cited Health line article medically reviewed by Eloise Theisen RN, MSN, AGPCNOP-BC dated April 23 2024.
THC, the main psychoactive component of cannabis, may only be detectable in saliva and oral fluid for 2–24 hours in most cases.
Most cannabis drug tests yield a positive result when the concentration of THC-COOH in urine exceeds 50 ng/mL.
A drug, if present in the urine specimen below its cut-off concentration, will not saturate the binding sites of its specific antibody.
False positives have been known to be triggered by consuming hemp-seed bars, low THC cannabis and CBD supplements, although the more detailed, more expensive gas chromatography-mass spectrometer (GCMS) test can tell the difference.
[11] In 2011, researchers at John Jay College of Criminal Justice reported that dietary zinc supplements can mask the presence of THC and other drugs in urine.
[12] However, a 2013 study conducted by researchers at the University of Utah School of Medicine refute the possibility of self-administered zinc producing false-negative urine drug tests.
[18][19] Other Azo dyes which are suitable for cannabinoid detection, albeit inferior to Fast Blue B/BB, include Corinth V, Blue LGC, Garnet GC (GR), Red AV, Garnet GBO, Bordeaux GP, and Red P.[19] In 1911, Dr. W. Beam discovered that the tissue of hemp, which is typically low in THC but high in CBD, gives a purple color when treated with bases.
Hair drug testing measures the marijuana parent metabolite embedded inside the hairshaft and eliminates external contamination as a source of a positive result.
[citation needed] Urine contains predominantly THC-COOH, while hair, oral fluid, and sweat contain primarily THC.
[26][27][28] Although unlikely to be used in court, electroencephalography (EEG) results show somewhat more persistent alpha waves of slightly lower frequency than the norm.