A study conducted in a warm climate does not automatically validate ethanol interpretation in advanced decomposition or unrefrigerated specimens. De Martinis and colleagues compared five specimen types in Brazil, but the 21 selected cases were sampled only 3–8 hours after death, had minimal decomposition and were refrigerated before analysis. Those conditions define the reach of the findings.
The study population was narrower than its setting
Investigators collected specimens in 103 autopsy cases at the Legal Medicine Center in Ribeirão Preto, Brazil, during May–December 2003. Twenty-one cases were selected for analysis because vitreous ethanol reached at least 0.1 g/L. Eight were classified as natural deaths and 13 as violent deaths.
The average sampling interval was six hours after death. Selecting on vitreous positivity means this was not an unbiased evaluation of all possible blood–vitreous combinations, particularly blood-positive cases with little or no vitreous ethanol. It also was not a study following bodies through progressively advanced decay.
Specimens were collected and handled under stated conditions
Femoral and subclavian blood, urine and right-eye vitreous were collected before the autopsy examination began; heart blood was collected separately during the examination. Peripheral blood was obtained by external percutaneous puncture into tubes containing EDTA and sodium fluoride. Urine was obtained by puncture toward the bladder, and approximately 2 mL vitreous was collected into an unpreserved tube.
The same person collected all specimens for each case, and specimens from that case were analyzed simultaneously. They were refrigerated at 4°C for two days before analysis. The study therefore cannot be described as testing the effects of long transport without refrigeration merely because the authors discussed that practical concern.
What the comparisons actually found
Ethanol was measured in duplicate by headspace gas chromatography with flame-ionization detection, using isobutanol as internal standard. The paper describes the preparation and instrumental conditions but does not provide a complete numerical method-validation dataset for detection limits, quantification limits, recovery and imprecision.
The authors reported no significant differences among blood collection sites and described strong correlations between specimen types. Table 3 gives vitreous correlations of 0.93 with heart blood, 0.98 with subclavian blood, 0.96 with femoral blood and 0.98 with urine; the reported correlation tests were significant at P < 0.05.
The abstract gives somewhat different correlation coefficients. Those values should not be silently combined or treated as identical. More fundamentally, a significant correlation tests association; it does not demonstrate individual interchangeability or identify how much ethanol was formed after death.
Why climate is not the experimental variable
The authors discussed local temperatures and the practical importance of alternative specimens in warm settings. They did not randomly allocate specimens to different temperatures, compare refrigerated with unrefrigerated transport, or measure microbial ethanol production over time. No temperature-specific production rate follows from the results.
The reported nonsignificant site differences also do not establish equivalence for every case. This small selected series and its early sampling window cannot settle what happens after several days of decomposition, extensive trauma or uncertain storage. The authors themselves called for larger studies and longer intervals after death.
Use the actual conditions when comparing a case
When a study is offered to support interpretation of a decomposed specimen, compare the interval, preservation and handling rather than its country alone. Ask whether the research measured specimen agreement, chemical stability or actual microbial formation; these are different questions.
The study supports useful early postmortem comparisons under its stated conditions. It does not establish impairment, a fatal ethanol concentration or the fraction attributable to drinking in an individual. For experimental evidence that directly tested tissue decomposition stages, see decomposition stage and ethanol formation.
Primary source
De Martinis BS, de Paula CMC, Braga A, Moreira HT, Martin CCS. Alcohol distribution in different postmortem body fluids. Human & Experimental Toxicology. 2006;25:93–97. doi:10.1191/0960327106ht596oa.
Leave a Reply