Subclavian blood should not automatically be interpreted as equivalent to femoral blood after death. In Prouty and Anderson’s primary investigation, subclavian drug concentrations generally tracked heart blood more closely than femoral blood, with important exceptions. Calling both specimens “peripheral” can conceal a material difference in what was actually collected.
What the investigators compared
The 1990 investigation combined sequential sampling, earlier field collections and comparisons among autopsy sites. Its subclavian comparison, Table 9, lists 17 distinct cases, with more than one drug or metabolite in several cases and some missing specimens. Those rows are not an equal-sized independent cohort for every analyte.
The sites were subclavian vein, femoral vein and heart blood. The broader phase protocol included left and right specimens, removed the chest plate before initial sampling, and repeated collections at least two hours apart. Consequently, the publication should not be presented as a controlled experiment in which all specimens came from intact bodies at one standardized interval after death.
A large difference can occur within one decedent
In case A-2408, Table 9 reports amitriptyline concentrations of 3.0 mg/L in subclavian blood, 0.14 mg/L in femoral blood and 2.1 mg/L in heart blood. The reported subclavian-to-femoral ratio was 21.4. Propoxyphene in that case measured 4.6, 0.46 and 4.2 mg/L, respectively, producing a subclavian-to-femoral ratio of 10.0.
These are individual observations, not typical ratios or correction factors. They show why replacing an anatomical description with a broad category can change the apparent significance of a result. A laboratory could measure both specimens accurately while the two numbers answer different specimen-specific questions.
The pattern was not universal
Case A-1087 provides a useful counterexample. Table 9 lists amoxapine at 2.0 mg/L in subclavian blood, 2.5 mg/L in femoral blood and 3.9 mg/L in heart blood. The subclavian-to-femoral ratio was 0.80. The study therefore does not establish that subclavian blood must always exceed femoral blood.
The authors describe a general site-dependent pattern, rather than a statistically validated conversion equation for each drug. Differences among analytes, cases, collection times and available specimens prevent a universal substitution rule. None of these three postmortem sites supplies an antemortem reference concentration merely by being included in the comparison.
Collection technique also affects the specimen
The authors advised ligating a peripheral vessel and withdrawing blood distal to the ligation when possible. They also reported observing rising concentrations during serial sampling from nonligated femoral veins until values approached those of vena cava blood. They did not provide a controlled sample size or a numerical mixing correction for that observation.
This is a reason to recover the collection record: exact vessel, side, incision or puncture technique, ligation, volume and timing. It is not proof that a particular femoral specimen was contaminated or that every case in the paper used a ligated vessel.
Analytical precision does not establish specimen equivalence
Antidepressants were measured using an earlier published method and subsequently an in-house HPLC method; most other drugs were measured by gas chromatography. Specimens were generally assayed in duplicate, with repeats when duplicate results differed by more than 10%; reported coefficients of variation were typically below 10%. These characteristics address measurement repeatability. They do not remove anatomical differences or validate a reconstruction of the dose taken.
For the separate question of whether peripheral blood preserves a predeath concentration, see femoral blood and earlier tricyclic antidepressant results. A site comparison alone cannot establish impairment, an administered dose or a drug’s contribution to death.
Primary source
Prouty RW, Anderson WH. The Forensic Science Implications of Site and Temporal Influences on Postmortem Blood-Drug Concentrations. Journal of Forensic Sciences. 1990;35(2):243–270. doi:10.1520/JFS12828J.
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