Unquantifiable Postmortem Cannabinoid Results Were Not Negative Results
Some postmortem specimens could not be quantified because matrix interference compromised the analysis. The paper distinguished those results from values below the quantification limit.
The analytical failures were explicit
In the nineteen-case series, decomposition-related or other in-vitro breakdown products affected chromatography in some stored specimens. Repeat analyses and reduced sample volume helped in some cases. THC remained unquantifiable in two cases and 11-hydroxy-THC in one because poor internal-standard recovery persisted.
The result categories answered different questions
A below-limit result describes the method’s quantitative boundary for that specimen under its criteria. An unavailable value caused by matrix interference means the analysis did not yield an acceptable concentration. Treating both as zero would manufacture data and distort detection proportions or central-to-peripheral ratios. The table used separate labels for these categories.
What another case requires
The study does not prove that every decomposed sample is unusable or that another laboratory’s result is wrong. Review chromatographic quality, internal-standard recovery, preparation changes and the final reporting decision. A valid numerical result still needs separate interpretation for sampling site, postmortem interval and cause of death. An unquantifiable result supplies neither a negative exposure finding nor an impairment conclusion.
Related analysis: the limits of central-to-peripheral ratios.
Research cited
Holland and colleagues (2011). Postmortem redistribution of THC, 11-hydroxy-THC, and THCCOOH. DOI: 10.1016/j.forsciint.2011.06.028.
