GHB can increase after collection in stored postmortem blood from people with no suspected GHB use. Beránková and colleagues demonstrated substantial, sometimes temporary changes during storage. A later measured concentration therefore cannot automatically be assigned to an administered dose or assumed to equal the concentration at autopsy.
The pooled experiment had a small biological denominator
The 2006 study’s first experiment followed material for eight months under four conditions: 4°C or −20°C, each with or without 1% weight/volume sodium fluoride. Postmortem femoral blood came from one decedent; postmortem urine was pooled from three. The antemortem comparison used serum pooled from four people and urine from one person. These were not large matched populations.
Postmortem material was collected at routine autopsy within two days after death, with the experiment beginning no later than five days after death. Repeated extracts were technical measurements of the same source material, not additional independent decedents.
Refrigerated, unpreserved blood showed a substantial rise
In the postmortem blood stored at 4°C without fluoride, the four-month result was 99.0 ± 16.6 mg/L, based on triplicate measurement and reported standard deviation. Concentrations subsequently declined; the eight-month value was 15.8 ± 6.6 mg/L. The changes were not a monotonic accumulation that could be extrapolated backward at a fixed rate.
Fluoridation and freezing generally inhibited formation, but neither should be summarized as guaranteeing a zero result. The refrigerated fluoridated blood had an initial reported value of 51.2 mg/L after one day, followed by much lower values. Frozen blood also showed occasional measurable concentrations. The authors could not determine that either freezing or fluoride was uniformly the more effective intervention across their experiments.
The individual-specimen experiment adds a different limitation
Twenty individual postmortem femoral-blood specimens were collected at autopsy approximately three days after death. The methods describe 16–27 days of refrigerated storage without preservative before the first analysis and addition of fluoride. They were then stored at 4°C for another four months.
Some specimens showed a temporary increase around the two-month measurement and later declined. By four months, the highest reported concentration was 6.5 mg/L. Adding preservative late cannot establish what happened during the earlier unpreserved interval, and the sparse later time points cannot recover an individual specimen’s complete concentration history.
Quantitation has method-specific uncertainty
The investigators used extraction, derivatization and GC–MS in selected-ion monitoring, with adipic acid as internal standard and matrix-specific calibration. The reported quantification limits were 3 mg/L for blood and serum and 0.5 mg/L for urine. Detection and quantification limits were not separately differentiated.
Intra-assay CV was 21% in postmortem blood and 22% in bovine serum at 50 mg/L, compared with 5% in urine at 20 mg/L. These are material precision limits. An unreported or below-limit value is not proof that GHB was absent, and small numerical differences should not be overinterpreted.
What the study permits an expert to conclude
The finding supports investigating storage-related formation when interpreting postmortem GHB. It does not establish that every positive result is artifactual, that known ingestion can be excluded, or that the observed concentrations define a universal endogenous/exogenous cutoff. The subjects had no suspected use; this was not independent proof of zero lifetime or recent exposure.
Obtain the collection site, interval, initial result, preservative timing, storage temperatures and analytical records. Keep specimen chemistry separate from impairment and cause-of-death attribution. The general need to distinguish detection from quantitative interpretation is also illustrated by alternative-matrix drug screening.
Primary source
Beránková K, Mutnanská K, Balíková M. Gamma-hydroxybutyric acid stability and formation in blood and urine. Forensic Science International. 2006;161:158–162. doi:10.1016/j.forsciint.2006.01.017.
Leave a Reply