Trends in central/peripheral ratio of fentanyl in Harris County, TX, and Orange County, CA, from 2009 to 2020

Since the opioid epidemic was declared in 2017, postmortem fentanyl cases and the need for interpretation of their results have increased. Postmortem redistribution (PMR) is one of the factors to consider when interpreting cases. There have been several previous studies regarding fentanyl PMR; however, these studies either have small sample sizes or were conducted prior to the declaration of the opioid epidemic, which may cause conflicting results and not be reflective of current trends. This study includes fentanyl central/peripheral (C/P) blood ratios from 748 cases from both Harris County, TX, and Orange County, TX, spanning from January 2009 to June 2022. Because the data set was determined to be non-normally distributed, a Kruskal-Wallis test was used for statistical comparisons. There were statistically significant differences between epidemic cases from the Harris County Institute of Forensic Sciences and the Orange County Crime Laboratory, C/P ratios from pre-epidemic to epidemic years, and in cases where medically related administration of fentanyl was documented when compared to cases where there was no documentation of licit fentanyl use. Various factors that could impact PMR were evaluated (age, gender, polydrug use, etc.), and no clear trend or observation was made from the data. Based on the results of this study, there is still no clear indication as to what caused the increase in C/P ratios, but it may be related to an increase in illicit fentanyl use.