Assessment of the stability of exogenous gamma hydroxybutyric acid (GHB) in stored blood and urine specimens

F.P. Busardò, S. Zaami, G. Baglio, F. Indorato, A. Montana, N. Giarratana, C. Kyriakou, E. Marinelli, G. Romano

Department of Anatomical, Histological, Forensic and Orthopedic Sciences, Sapienza University of Rome, Rome, Italy. simona.zaami@uniroma1.it

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• Toxicology

OBJECTIVE: The aim of this work is to test the stability of exogenous GHB in whole blood and urine samples collected from living and deceased GHB free-users, spiked with known concentrations of GHB and stored at different temperatures (–20°C, 4°C and 20°C) up to 4 weeks.

MATERIALS AND METHODS: GHB was added to GHB-free ante-mortem blood and urine samples at the concentration of 5 and 10 mg/L, respectively whereas in post-mortem blood and urine specimens at 50 and 10 mg/L respectively. All samples were stored at three different temperatures: –20°C, 4°C and 20°C and extracted and analyzed at three days, 1 week, 2 weeks, 3 and 4 weeks in duplicate. No preservatives were added. GHB was quantified by GC-MS after LLE according to a previously published method.

RESULTS: Post-mortem blood specimens showed a reduction of GHB levels higher than 10% only after a period of 4 weeks of storage for samples kept at +4°C and +20°C, whereas samples stored at –20°C showed a mean reduction of 8.7%. In post-mortem urine samples, there was a mean reduction of GHB levels higher than 20% at all storage temperatures, after 4 weeks of storage. Ante-mortem blood samples showed a reduction of GHB levels lower than 10% only after 3 days of storage at –20°C and at +4°C (samples stored at +20°C showed a mean reduction of 10.4%). After 4 weeks of storage, there was a mean reduction of GHB concentrations higher than 20% at all storage temperatures. Ante-mortem urine samples showed a reduction of GHB levels higher than 10% after just 3 days of storage for samples kept at all tested temperatures. After 4 weeks of storage, there was a mean reduction of GHB concentrations higher than 25% at all storage temperatures.

CONCLUSIONS: According to our findings, it would be useful to perform GHB analysis both in blood and urine specimens within 3 days of sampling and the specimens should be stored at –20°C or 4°C in order to avoid instability issues.

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