The Saliva Panel’s High THC Range Did Not Apply to Every Cannabinoid
The assay’s upper quantitative range extended to 2,000 ng/mL for THC but only 200 ng/mL for the other panel members. A panel-wide claim of a 2,000 ng/mL range would therefore misstate its validation.
The ranges were analyte-specific
The ten-analyte method had lower quantification limits of either 0.4 or 1 ng/mL, depending on the compound. The upper range was also compound-specific: THC received the extended range. The investigators separately challenged a one-to-ten dilution of a fortified high-THC specimen and reported acceptable THC quantification after dilution.
Detection is not unlimited quantification
An instrument can produce a visible signal beyond a validated calibration range without demonstrating an accurate concentration there. A high result requires the laboratory’s applicable range and any validated dilution procedure. The THC dilution result should not silently become evidence that all ten analytes can be diluted or quantified identically.
What the range tells a reviewer
The extended THC range addresses an analytical challenge in oral fluid. It does not establish a biological threshold, a saliva-to-blood conversion or a degree of impairment. A review should name the analyte, actual calibration range, preparation and handling of out-of-range results. The small clinical illustration in this method paper supplies no universal dose-response rule that can replace those checks.
Related analysis: the oral-fluid assay’s small human illustration.
Research cited
Sobolesky and colleagues (2019). Validation of a liquid chromatography-tandem mass spectrometry method for analyzing cannabinoids in oral fluid. DOI: 10.1016/j.cca.2019.01.002.
