The challenge of post-mortem GHB analysis: storage conditions and specimen types are both important

For the interpretation of concentrations of gamma-hydroxybutyrate (GHB) in post-mortem specimens, a possible increase due to post-mortem generation in the body and in vitro has to be considered. The influence of different storage conditions and the specimen type was investigated.

Post-mortem GHB concentrations in femoral venous blood (VB), heart blood (HB), serum (S) from VB, urine (U), cerebrospinal fluid (CSF) and vitreous humour (VH) were determined by gas chromatography-mass spectrometry after derivatisation. Various storage conditions, that is 4 °C or room temperature (RT) and the addition of sodium fluoride (NaF), were compared during storage up to 30 days. Additionally, bacterial colonisation was determined by mass spectrometry fingerprinting.

Twenty-six cases without involvement of exogenous GHB were examined. GHB concentrations (by specimen) at day 0 were 3.9-22.1 mg/L (VB), 6.6-33.3 mg/L (HB), < 0.5-18.1 mg/L (U), 1.1-10.4 mg/L (CSF) and 1.7-22.0 mg/L (VH). At 4 °C, concentrations increased at day 30 to 5.6-74.5 mg/L (VB), 4.6-76.5 mg/L (HB) and < 0.5-21.3 mg/L (U). At RT, concentrations rose to < 0.5-38.5 mg/L (VB), 1.2-94.6 mg/L (HB) and < 0.5-37.5 mg/L (U) at day 30. In CSF, at RT, an increase up to < 0.5-21.2 mg/L was measured, and at 4 °C, a decrease occurred (< 0.5-6.5 mg/L). GHB concentrations in VH remained stable at both temperatures (1.2-20.9 mg/L and < 0.5-26.2 mg/L). The increase of GHB in HB samples with NaF was significantly lower than that without preservation. No correlation was found between the bacterial colonisation and extent of GHB concentration changes.

GHB concentrations can significantly increase in post-mortem HB, VB and U samples, depending on storage time, temperature and inter-individual differences. Results in CSF, VH, S and/or specimens with NaF are less affected.