DTI/DXI interferences with global coagulation tests in emergency hospital admissions - Results of the prospective Dresden NOAC Registry (NCT01588119)

Background: Depending on test assays and the time of last DOAC intake, direct thrombin inhibitors (DTI) and direct FXa inhibitors (DXI) may or may not affect prothrombin time (PT), international normalized ratio (INR) or activated thromboplastin time (aPTT) but the clinical impact is unknown. Methods: Using data from the Dresden NOAC Registry, we evaluated the impact of DOAC on first PT, INR or aPTT tests during emergency hospitalizations of DTI/DXI patients and the assay performance across 50 coagulation laboratories. Results: In 724 emergency admissions (77 DTI; 647 DXI), 490 cases (67.7%) had a reported last DOAC intake within 12 h before blood sampling. INR and PT were elevated above the upper limit of normal (ULN) in >65% of all cases and aPTT was elevated in 45%. On the other hand, >30% of all cases had normal values of INR, PR and aPTT despite a DOAC intake within the last 12 h. Assay performance for detecting or ruling out therapeutic DOAC levels was highly variable and, overall, insufficient to guide clinical decisions. DOAC specific testing was performed in <10% of all cases. Conclusion: Many DOAC recipients present with elevated PT, INR or aPTT during emergency admissions but false negative values within 12 h of last intake as well as elevated values beyond 24 h after last DOAC intake are common. Both scenarios may result in clinical misinterpretation and, potentially, in patient harm, also because DOAC specific testing is rarely performed in emergency settings.