Short tandem repeat (STR) typing of a deceased individual with an extensive blood transfusion history: A case report

Detecting donor DNA in blood samples after multiple allogeneic transfusions remains a persistent concern in forensic human identification, given the limited and variable data. Although some studies have reported no secondary DNA profiles, transfusion-associated microchimerism (TA-MC) has been observed in deceased individuals who received perimortem blood transfusions. In this case report, we present autosomal short tandem repeat (aSTR) findings for a deceased male who received four units of plasma-reduced RBCs within 24 hours and 25 units over a period of eight months before his death. Given this extensive blood transfusion history, there was concern that donor DNA might persist and interfere with obtaining a reliable aSTR profile for paternity testing. To address this, we analyzed buccal swabs, skin, and muscle tissue, in addition to blood samples. No secondary aSTR profile was detected in the blood, and all four sample types produced concordant DNA profiles. In this instance, results suggest that any donor DNA present was below the detection threshold for STR analysis using capillary electrophoresis (CE) but may be detectable with more sensitive genotyping assays such as next generation sequencing (NGS) or digital PCR. Detection is more likely after a recent massive pRBC transfusion, the use of non-leukoreduced blood, or transfusion in leukopenic recipients. Despite the complications associated with massive allogeneic blood transfusions, aSTR typing remains a robust and reliable method for forensic human identification, particularly when suitable sample types are selected and rigorous procedures are followed in cases involving transfused individuals.