Testing antemortem blood samples for ethanol after four to seven years of refrigerated storage

Sample suitability and stability in different blood collection tubes for methanol, ethanol, isopropanol, acetone and glycols analysis

AIM

To systematically examine the sample suitability and stability for volatile alcohols (methanol, ethanol and isopropanol with its metabolite acetone) and glycols (ethylene/propylene glycols, EG/PG) in different collection tubes.

METHOD

Two pools of whole blood were created and spiked with two levels of volatile alcohols and EG/PG. The spiked whole blood was added to six different blood collection tubes and were kept at different storage conditions. An aliquot was prepared from baseline replicates. Concentrations of volatile alcohols and glycols were analysed by gas chromatography.

RESULTS

All blood collection tubes have demonstrated similar performance over different storage conditions, that is, to be statistically insignificant (p>0.05) with the only exception of PG at the high concentration of day 7 at 4°C condition (p<0.05 but clinically insignificant as

CONCLUSION

Grey/red/lavender, serum separator tube, plasma separator tube and the newly developed Barricor tubes are all suitable for volatile alcohols and EG/PG analysis. Primary samples are stable for 2 days room temperature, 14 days at 4°C and 28 days at -20°C for volatile alcohols, and 2 days room temperature, 7 days at 4°C, and 28 days at -20°C for EG. Aliquoted samples are stable up to 28 days at -20°C for all volatile alcohols and glycols.

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Key Words

• BIOCHEMISTRY
• Chemistry, Clinical
• Diagnostic Techniques and Procedures
• TOXICOLOGY

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MESH Headings

• Humans
• Acetone/analysis
• Acetone/blood
• 2-Propanol
• Blood Specimen Collection/instrumentation
• Blood Specimen Collection/methods
• Methanol/chemistry
• Ethanol/blood
• Ethanol/analysis
• Chromatography, Gas/methods
• Glycols
• Time Factors
• Specimen Handling/methods
• Specimen Handling/instrumentation

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Affiliation(s)

Leonardo Cui Department of Laboratory Medicine, Dr. Everett Chalmers Regional Hospital, Horizon Health Network, Fredericton, New Brunswick, Canada Neuroscience Program, University of Western Ontario, London, Ontario, Canada
John G Swanwick Department of Laboratory Medicine, Dr. Everett Chalmers Regional Hospital, Horizon Health Network, Fredericton, New Brunswick, Canada
Yu Chen Department of Laboratory Medicine, Dr. Everett Chalmers Regional Hospital, Horizon Health Network, Fredericton, New Brunswick, Canada Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada Discipline of Laboratory Medicine, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada

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Blood alcohol concentration in the clinical laboratory: a narrative review of the preanalytical phase in diagnostic and forensic testing

The analysis of blood alcohol concentration (BAC), a pivotal toxicological test, concerns acute alcohol intoxication (AAI) and driving under the influence (DUI). As such, BAC presents an organizational challenge for clinical laboratories, with unique complexities due to the need for forensic defensibility as part of the diagnostic process. Unfortunately, a significant number of scientific investigations dealing with the subject present discrepancies that make it difficult to identify optimal practices in sample collection, transportation, handling, and preparation. This review provides a systematic analysis of the preanalytical phase of BAC that aims to identify and explain the chemical, physiological, and pharmacological mechanisms underlying controllable operational factors. Nevertheless, it seeks evidence for the necessity to separate preanalytical processes for diagnostic and forensic BAC testing. In this regard, the main finding of this review is that no literature evidence supports the necessity to differentiate preanalytical procedures for AAI and DUI, except for the traceability throughout the chain of custody. In fact, adhering to correct preanalytical procedures provided by official bodies such as European federation of clinical chemistry and laboratory medicine for routine phlebotomy ensures both diagnostic accuracy and forensic defensibility of BAC. This is shown to depend on the capability of modern pre-evacuated sterile collection tubes to control major factors influencing BAC, namely non-enzymatic oxidation and microbial contamination. While certain restrictions become obsolete with such devices, as the use of sodium fluoride (NaF) for specific preservation of forensic BAC, this review reinforces the recommendation to use non-alcoholic disinfectants as a means to achieve "error-proof" procedures in challenging operational environments like the emergency department.

Preanalytical factors influencing the results of ethanol analysis in postmortem specimens

Excessive drinking and drunkenness are underlying factors in many fatal accidents, which make the quantitative determination of ethanol in postmortem (PM) specimens an essential part of all unnatural death investigations. The same analytical methods are used to determine ethanol in blood taken from living and deceased persons although the interpretation of the results is more complicated in medical examiner cases owing to various preanalytical factors. The biggest problem is that under anaerobic conditions ethanol can be produced naturally in decomposed bodies by microbial activity and fermentation of blood glucose. Ways are needed to differentiate antemortem ingestion of ethanol from PM synthesis. One approach involves the determination of ethanol in alternative specimens, such as bile, cerebrospinal fluid, vitreous humor and/or urine, and comparison of results with blood alcohol concentration (BAC). Another approach involves the analysis of various alcohol biomarkers, such as ethyl glucuronide, ethyl sulfate and/or phosphatidylethanol or the urinary metabolites of serotonin 5-hydroxytryptophol/5-hydroxyindoleacetic acid (5-HTOL/5-HIAA). If ethanol had been produced in the body by microbial activity, the blood samples should also contain other low-molecular volatiles, such as acetaldehyde, n-propanol and/or n-butanol. The inclusion of 1-2% w/v sodium or potassium fluoride, as an enzyme inhibitor, in all PM specimens is essential to diminish the risk of ethanol being generated after sampling, such as during shipment and storage prior to analysis. Furthermore, much might be gained if the analytical cut-off for reporting positive BAC was raised from 0.01 to 0.02 g% when PM blood is analyzed. During putrefaction low BACs are more often produced after death than high BACs. Therefore, when the cadaver is obviously decomposed, a pragmatic approach would be to subtract 0.05 g% from the mean analytical result. Any remaining BAC is expected to give a more reliable indication of whether alcohol had been consumed before death.

Comparisons of blood alcohol concentrations between initial testing and reanalysis from unopened tubes preserved with 0.25% NaF following refrigerated storage up to 3.93 years

Few studies support the usage of <1% nominal sodium fluoride (NaF) to preserve ethanol in antemortem blood. Of these studies, several are limited by short study durations of 90 days or less, and there is limited research of authentic samples preserved with <1% NaF. In this retrospective analysis, data from initial and reanalysis testing of blood alcohol concentration (BAC) in antemortem blood collected in 6 mL gray-top tubes (providing 0.25% nominal NaF) has been compiled, to evaluate changes in ethanol concentration that occurred after periods of refrigerated storage. The time between initial and reanalysis was determined by court request(s), and ranged 0.30-3.93 years. In each case, a previously unopened tube was selected for reanalysis testing. Comparable BAC values were found from initial testing, with BACs ranging from 0.025 to 0.394 g/100 mL, and reanalysis testing, with BACs ranging from 0.021 to 0.393 g/100 mL. Ethanol changes ranged from -0.013 g/100 mL (decrease) to 0.008 g/100 mL (increase). BAC reanalysis values that increased (n = 6) were within the uncertainty of measurement (UM) from the initial BAC test, that is, were not statistically or analytically significant. For BAC decreases (n = 29), four test values exceeded the UM of the original test, with BAC losses ranging from 0.004 to 0.011 g/100 mL (relative percent changes 6.5-16.0% loss). The average ethanol change was -0.004 g/100 mL, which is comparable to or less than ethanol losses from studies using 1% NaF preservative of varying temperature and storage duration.