No. A central-to-peripheral fentanyl ratio near one shows similarity between two postmortem specimens; it does not establish that either concentration equals the concentration during life. An Orange County study illustrates why both the individual range and the collection procedures matter.
What the paired results showed
Havro and colleagues reviewed fentanyl-positive casework from 2018–2019. Their death-investigation dataset included 285 central blood specimens. Peripheral blood was tested in a selected subset of 58 cases, giving 58 central/peripheral pairs.
The central/peripheral ratio had a median of 1.03 and mean of 1.83. Individual ratios ranged from 0.14 to 9.52. The median therefore concealed substantial variation, including cases in which the peripheral result exceeded the central result.
The authors interpreted these ratios as indicating little redistribution in their reviewed material. That conclusion concerns the distribution between sampled postmortem compartments. Without a paired antemortem specimen, a ratio near one cannot demonstrate that neither compartment changed after death.
How were the specimens collected?
Central blood was collected near the central heart cavity at autopsy and refrigerated at 4°C in amber glass bottles. Peripheral specimens were described as coming from a femoral or clavicle artery and were frozen at −20°C in glass tubes. The exact location and mechanism of those draws were not specified.
Blood contained sodium fluoride and potassium oxalate, approximately 2% and 0.75%, respectively, when containers were filled to capacity. These collection and storage differences are part of the comparison. The paper did not provide a uniform death-to-collection interval for the paired subset.
Further peripheral or tissue analysis could be performed when initially detected drugs might have contributed to death and were known to redistribute. The 58 pairs were consequently not a random sample of all deaths or all fentanyl-positive specimens.
What tissue results added
The study also reported 55 brain and 16 liver specimens. Brain fentanyl ranged from 1.9 to 441 ng/g, while liver ranged from 11.6 to 226 ng/g. Those tissue units must remain distinct from blood concentrations in ng/mL.
Fifteen liver/peripheral pairs had a mean ratio of 6.78, median of 6.20 and range of 1.90–11.7. Dividing tissue ng/g by blood ng/mL produces mL/g, numerically equivalent to L/kg. It is not a dimensionless blood-to-blood ratio. These selected paired data do not establish a universal tissue-to-blood conversion or quantify a within-person change from life to death.
Screening and confirmation were separate
Initial screening used LC–quadrupole time-of-flight MS. Fentanyl was subsequently confirmed and quantified by LC–MS/MS, with duplicate measurements averaged for reporting. The quantitative calibration range was 0.5–32 ng/mL. The authors reported validated detection and quantification limits of 0.5 ng/mL and bias and precision within 20% at the tested validation conditions.
Those analytical findings support the measurement procedure. They do not establish biological equivalence between collection sites or identify the cause of an individual ratio difference.
What to retain in a case review
Keep both concentrations, both sites, preservation, handling and any sampling limitations. Review the full paired distribution rather than turning its median into a correction factor. A high or low ratio alone does not establish dose, impairment or cause of death.
For additional collection-site evidence, see subclavian versus femoral postmortem blood. That separate research also requires its own specimen and analyte context.
Primary source
Havro V, Casassa N, Andera K, Mata D. A Two-Year Review of Fentanyl in Driving under the Influence and Postmortem Cases in Orange County, CA, USA. Journal of Analytical Toxicology. 2022;46(8):875–881. doi:10.1093/jat/bkac030.
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