A low average liver-to-blood ratio can support a hypothesis that hydrocodone has relatively little potential for postmortem redistribution. It cannot guarantee that every case follows that pattern or reconstruct a person’s concentration before death. A 39-case study illustrates the distinction: one high ratio persisted on repeat testing but was excluded from the reported summary ratio.
Which cases and specimens were studied?
Saitman, Fitzgerald and McIntyre examined 39 cases with hydrocodone detected in peripheral blood and sufficient central blood and liver for comparison. Cases came from the San Diego Medical Examiner’s Office between October 2013 and June 2014. Autopsy occurred within 48 hours of recorded death; the exact time of death was not established in every case.
Cases with obvious decomposition or severe trauma were excluded, as were cases with a known long delay between actual and recorded death. These restrictions matter when applying the results to a decomposed body or a substantially different postmortem interval.
Peripheral blood was collected from the common iliac veins, rather than necessarily from a femoral site. Central blood came from the heart or adjacent great vessels. Approximately 20 mL of peripheral blood was collected into standard 10 mL glass tubes, each containing 100 mg sodium fluoride and 20 mg potassium oxalate. Central blood was placed in identical tubes. Unpreserved liver came from the right upper lobe. Specimens were refrigerated at 4°C until analysis, and each case’s three matrices were tested in the same analytical run.
How was hydrocodone measured?
The study used solid-phase extraction, derivatization and GC–MS, with identification based on retention time and ion ratios. The blood calibration range was 0.02–1.0 mg/L, the detection limit 0.01 mg/L and the quantification limit 0.02 mg/L. Liver specimens were diluted to fall within the calibration range.
Analytical performance was not identical at every concentration. A nominal 0.10 mg/L blood control measured 0.087 ± 0.003 mg/L in five study runs. A 0.40 mg/kg liver control measured 0.41 ± 0.02 mg/kg in four runs. These are method-performance observations, separate from the interpretive question of redistribution.
The general pattern and its exception
Central and peripheral blood concentrations were strongly correlated, with R² = 0.965. The central/peripheral ratio averaged 1.3 ± 0.35, with a median of 1.2. Central concentrations were nevertheless statistically higher than peripheral concentrations in the paired comparison, p = 0.0021. Strong correlation therefore did not mean equality between collection sites.
After exclusion of one outlier, liver and peripheral blood correlated with R² = 0.915, and the liver/peripheral ratio averaged 3.4 ± 1.7 L/kg, with a median of 3.0 L/kg. The units matter: liver was measured in mg/kg and blood in mg/L, so their ratio has units of L/kg.
The excluded case had liver hydrocodone of 2.0 mg/kg and peripheral blood of 0.10 mg/L, a ratio of 20 L/kg. Repeat analysis produced a ratio of approximately 19 L/kg. The authors excluded it using Dixon’s Q test. Repetition did not establish why the case differed, but it means the high ratio should not simply disappear from a discussion of the study’s practical limits.
Why this is not an antemortem correction formula
The authors interpreted the generally low liver/peripheral ratios as evidence of minimal redistribution potential. However, all three specimens were postmortem. There were no paired antemortem measurements to show how much any individual’s concentration changed between life and autopsy.
A ratio below a proposed value is therefore not proof that an autopsy blood concentration equals the concentration during life. Nor can the repeated high ratio, by itself, quantify a redistribution effect. Specimen distribution, analytical variation and case circumstances need evaluation without assuming a single mechanism.
For case review, retain the exact blood collection site, both underlying concentrations, ratio units and any excluded observations. Drug detection and concentration alone do not establish dose, impairment or cause of death. See also why co-detected drugs can have different postmortem distributions.
Primary source
Saitman A, Fitzgerald RL, McIntyre IM. Evaluation and comparison of postmortem hydrocodone concentrations in peripheral blood, central blood and liver specimens: A minimal potential for redistribution. Forensic Science International. 2015;247:36–40. doi:10.1016/j.forsciint.2014.11.031.
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