Longitudinal assessment of DNA recovery from post-mortem whole blood stored in EDTA, sodium fluoride/potassium oxalate and additive-free tubes

Adverse drug reactions and fatalities can result from therapeutic drug use due to genetic deficiencies in drug-metabolizing enzymes. In cases where ancillary testing may not reveal a clear cause of death, molecular autopsies can be valuable. However, forensic mortuaries do not retain DNA samples in all cases, which hinders subsequent genetic testing if it is later deemed necessary. This study aimed to evaluate whether post-mortem whole blood samples collected for toxicological analysis, could provide viable DNA for genetic testing after varying storage periods. Thirty deceased individuals were recruited with informed consent. Blood collected at autopsy from each individual was stored in two sodium fluoride/potassium oxalate (gray-top) tubes, two additive-free (red-top) tubes and one ethylenediaminetetraacetic acid (EDTA; purple-top) tube- the latter recommended for DNA analysis. Blood from one gray-top and one red-top tube were sampled for toxicological analysis prior to DNA analysis, while the remaining samples (acting as controls) underwent DNA analysis immediately. DNA analysis involved DNA extraction and DNA concentration and degradation assessment. Blood samples were stored at 4 °C and DNA extraction and analysis was repeated one year and then five years later. Toxicological sampling did not significantly influence DNA results. DNA concentration and quality significantly decreased over time for all sample types, with DNA from red-top tubes showing the greatest decline. The study showed that DNA testing for drug-metabolizing enzymes was feasible on whole blood that had been stored for five years. This finding supports the potential for retrospective genetic testing in cases of adverse drug reactions and fatalities.