Blood collected while a patient is alive can provide valuable evidence in a later death investigation, but a hospital serum ethanol result and a forensic whole-blood result are not automatically interchangeable. Saitman and colleagues found strong correlation alongside significant bias in 39 paired case comparisons. That combination makes the specimen and method essential parts of the interpretation.
These were antemortem specimens analyzed in death casework
The investigators reviewed a reported 15-month period of San Diego County Medical Examiner toxicology work. Of 2,321 cases, 280 involved hospital antemortem specimens, 59 screened positive for ethanol, and 39 had sufficient suitable original material for the quantitative comparison. The specimens were collected at hospital admission before death, rather than paired autopsy blood drawn later.
This distinction limits what the study can show about postmortem ethanol formation. It demonstrates the utility and complications of recovering predeath specimens; it did not experimentally measure microbial ethanol production in decomposing bodies.
Hospital results were from serum, whereas the forensic laboratory generally analyzed whole blood and used serum in four cases. Most received whole-blood specimens were in EDTA tubes, although sodium citrate and sodium fluoride tubes also occurred. Specimens were stored at 4°C after arrival at the medical examiner’s office. The maximum interval between hospital and forensic testing was ten days. A uniform venipuncture site was not specified.
Different methods can produce correlated but biased results
The hospital method was enzymatic alcohol-dehydrogenase testing, measuring a spectrophotometric response associated with NADH production. Forensic testing used headspace gas chromatography with flame-ionization detection. The forensic screen used a single calibrator and one column; subsequent quantitation used three calibrators, a different column, duplicate testing and averaged results. These were distinct analytical stages.
The overall R² between hospital and forensic results was 0.942. Yet forensic results showed an average negative bias of 14.1% relative to hospital results, and the paired difference was statistically significant (P < 0.0001). Larger percentage differences occurred below 0.10 g/dL. The authors attributed the findings potentially to matrix, method and calibration differences; the design did not isolate one cause for the entire bias.
Accordingly, 14.1% is a study finding, not a universal correction factor. It would be inappropriate to subtract that percentage from every hospital result without specimen- and method-specific support.
Sample identity can matter more than the regression
One discrepant case had a hospital value of approximately 0.34 g/dL and a forensic value of approximately 0.20 g/dL. Excluding that case increased R² to 0.981. The authors suspected different samples may have been analyzed, but did not prove a switch. This uncertainty should remain visible rather than being treated as a confirmed laboratory error or silently discarded.
Hospitals differed in collection practice, tube selection and analytical procedure. The article also describes contamination examples outside the 39-case ethanol cohort, including isopropanol and material associated with separator tubes. Those examples are reasons to investigate a questionable result, not estimates of contamination prevalence in the study.
Performance characteristics do not resolve every interpretive issue
The forensic method reported a detection limit of 0.005 g/dL and quantification limit of 0.02 g/dL. Over nine months, control results averaged 0.077 g/dL for a 0.081 g/dL target and 0.198 g/dL for a 0.202 g/dL target, with CVs of 2.2% and 1.5%, respectively. These describe analytical performance under the reported conditions, not certainty about specimen identity or the concentration at an earlier event.
A useful case review preserves collection time, specimen type, tube and storage history, original laboratory records and exact units. It separates the measured antemortem concentration from any later postmortem change, and separates chemical concentration from impairment or cause of death. Our discussion of different alcohol-measurement compartments provides related context.
Primary source
Saitman A, Estrada J, Fitzgerald RL, McIntyre IM. Comparative analysis of hospital and forensic laboratory ethanol concentrations: A 15 month investigation of antemortem specimens. Journal of Forensic and Legal Medicine. 2015;33:23–27. doi:10.1016/j.jflm.2015.03.012.
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