Extrapolated THC Values Were Outside the Dried-Spot Method’s Validated Calibration Range
Some high THC results in the dried-blood-spot study were explicitly extrapolated beyond calibration. A printed concentration does not by itself establish that the concentration lies within the validated quantitative interval.
The range had lower and upper boundaries
The LC–MS/MS calibration range was 0.5–20 nanograms per milliliter for THC and 1.25–100 for THC-COOH. Among 159 dried spots, 19 THC results exceeded the upper THC limit, while 29 were below the lower limit. The paper labeled certain higher numerical values as extrapolated.
Detection, quantification and extrapolation differ
A signal may support detection without meeting the criteria for reliable numerical quantification. At the opposite end, estimating a value above the highest calibrator extends the fitted relationship beyond its demonstrated range. Neither situation should be silently described as an ordinary in-range measurement.
The reporting distinction matters near a disputed value
Review whether a laboratory diluted and reanalyzed a specimen under a validated procedure or reported an extrapolation. The study’s result cannot establish that every other laboratory handles high concentrations identically. Retaining the range and reporting category helps distinguish observed signal from the strength of its numerical interpretation. These analytical limits also do not become biological thresholds for intoxication or functional impairment.
Related analysis: the study’s broader findings and limitations.
