Quantification of direct‐acting oral anticoagulants: Application of a clinically validated liquid chromatography‐tandem mass spectrometry method to forensic cases

In certain forensic cases, a quantification of direct-acting oral anticoagulants (DOACs) can be necessary. We evaluate the applicability of a previously described liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodology for the determination of DOACs in plasma to postmortem specimen. Postmortem internal quality control (PIQC) samples were prepared in pooled blank postmortem heart blood, femoral blood, cerebrospinal fluid (CSF), and urine as well in plasma. To examine the application of the clinical method to forensic cases, the main validation parameters were reinvestigated using PIQC samples. Postmortem samples of 12 forensic cases with evidence of previous rivaroxaban intake and unknown bleeding disorders were analyzed. Interday variability remained within the acceptance criterion of ±15%. Matrix effects were comparable in blank plasma and postmortem matrix extracts. After 4 weeks of storage in the refrigerator, no relevant decrease of DOACs was evident. After 96 h of storage at room temperature, a slight decrease in edoxaban concentration was observed in CSF and urine, while plasma edoxaban decreased by about 50%. Median (range) rivaroxaban concentrations determined in specimen of forensic cases were as follows: heart blood (n = 6), 17.2 ng/ml (<LOQ, 56.6 ng/ml); femoral blood (n = 12), 27.6 ng/ml (<LOQ, 110.5 ng/ml); CSF (n = 7), 11.7 ng/ml (<LOQ, 17.5 ng/ml); urine (n = 6), 275.7 ng/ml (14.5-870.9 ng/ml). The median heart/femoral blood rivaroxaban ratio was 1.2 (n = 5). Exemplary, a forensic case with detection of edoxaban in femoral blood, CSF, and urine, is presented. DOACs can be detected in postmortem heart and femoral blood, CSF, and urine specimen by LC-MS/MS. Based on limited forensic cases, no significant redistribution was evident for rivaroxaban, which was found at highest concentrations in urine.