A GHB cutoff developed for carefully collected blood from living volunteers cannot simply be transferred to autopsy blood. Shima and colleagues proposed 1.0 µg/mL only under specified antemortem collection and storage conditions. Their experiment did not validate that value as a postmortem exposure threshold.
Who supplied the blood?
The 2005 study measured whole blood from 24 healthy Asian volunteers: 14 men and 10 women, aged 25–55 years. Blood was collected aseptically into vacuum-stoppered polyethylene tubes, immediately cooled and stored at −20°C without added preservative. Processing occurred within three hours of collection, followed by prompt analysis. The paper did not specify a vascular collection site.
These were living-person specimens, not blood recovered after death or decomposition. The small, selected healthy-volunteer sample also did not represent all possible medical conditions or drug exposures.
Initial GHB concentrations ranged from 0.005 to 0.010 µg/mL, averaging 0.0069 ± 0.0020 µg/mL. The investigators found no obvious male–female difference. In equivalent units, 0.005–0.010 µg/mL equals 0.005–0.010 mg/L, or 5–10 ng/mL. Switching unit labels without converting the numbers could produce a thousandfold error.
The method was designed to measure very low concentrations
The laboratory used protein precipitation, trimethylsilyl derivatization and GC–MS. Selected-ion monitoring was used for concentrations at or below 0.03 µg/mL. Quantitation used standard addition and 2-hydroxycaproic acid as internal standard.
Detection limits were 0.03 µg/mL in full-scan mode and 0.003 µg/mL in selected-ion monitoring. The reported linear range was 0.003–3.0 µg/mL. Recovery at a 1.0 µg/mL spike was 63%. A nominal 0.10 µg/mL control measured 0.096 ± 0.015 µg/mL in five measurements; reported within-day and between-day precisions were 5.3% and 6.1%.
These analytical characteristics explain how the study measured trace endogenous GHB. They are not the diagnostic sensitivity or specificity of an exposure cutoff.
Storage experiments did not reproduce autopsy conditions
The study also examined additives and storage. Anticoagulant experiments used three preparations per condition, rather than the full 24-person cohort. Sodium citrate and heparin produced larger increases than EDTA or sodium oxalate under the tested conditions.
The long-term experiment used blood from three healthy volunteers, stored under different temperature and preservative conditions. After 16 months, reported in-vitro production was below 0.03 µg/mL at −20°C and below 0.4 µg/mL at 4°C. Room-temperature increases were larger. Sodium azide showed no remarkable benefit during refrigerated storage in that experiment.
The authors did not establish a universal preservative recipe for postmortem specimens. Aseptic blood collected during life and blood exposed to postmortem biochemical and microbial changes present different problems.
The proposed cutoff had explicit conditions
The proposed 1.0 µg/mL value was limited to blood collected aseptically during life, stored at 4°C or below, examined within two weeks and interpreted after excluding GHB aciduria, a metabolic disorder. It was not a fatal-concentration threshold or a measure of impairment.
For a death investigation containing both hospital and autopsy specimens, the specimen’s origin and handling must travel with its result. This study supplies no formula for translating a hospital concentration into an autopsy concentration, or the reverse.
For a separate postmortem method issue, see how internal standards affected reported GHB concentrations. Both specimen context and measurement procedure matter.
Primary source
Shima N, Miki A, Kamata T, Katagi M, Tsuchihashi H. Endogenous Level and in Vitro Production of GHB in Blood from Healthy Humans, and the Interpretation of GHB Levels Detected in Antemortem Blood Samples. Journal of Health Science. 2005;51(2):147–154. doi:10.1248/jhs.51.147.
Leave a Reply