Fig. 1. Lupus anticoagulant (LA) results in COVID-19 patients with (black circles) and without thrombotic events (open squares). Patient dRVVT screen (Scr, low phospholipid concentration) and confirm (Conf, high phospholipid concentration) results were normalized, i.e. expressed as ratios against reference plasma results.Final results were expressed as screen ratio/confirm ratio. Cut-off value was 1.20 for both screen ratio and screen ratio/confirm ratio, demonstrating the phospholipodependence.

Introduction: Lupus Anticoagulant (LA) testing using dilute Russell Viper Venom Time (dRVVT) is challenging in patients receiving Direct Oral AntiCoagulants (DOAC) due to potential false positive results. In a multicenter study, we evaluated the in vitro removal of DOAC by activated charcoal (DOAC remove ®), allowing reliable dRVVT testing. Materials and Methods: Patient samples were analyzed before and after treatment with DOAC remove ® : 49 apixaban, 48 rivaroxaban, 24 dabigatran and 30 none. DOAC plasma concentrations were measured using anti-Xa or anti-IIa diluted thrombin time assays. In a subset of 28 samples, DOAC concentrations were also measured using HPLC-MS/MS following treatment with DOAC remove ®. DRVVT was performed using STA-Staclot dRVVT Screen ® /Confirm ® (Stago) or LAC-Screening ® /Confirm ® (Siemens). Results: Baseline median [min-max] concentrations were 94 [<20-479] for apixaban, 107 [<20-501] for rivaroxaban and 135 ng/mL [<20-792] for dabigatran; dRVVT screen ratio /confirm normalized ratio was positive in 47, 90 and 42 % of apixaban, rivaroxaban and dabigatran samples. Treatment with DOAC remove ® did not affect dRVVT results in non-DOAC patients while it resulted in DOAC concentrations < 20 ng/mL in 82, 98 and 100 % of samples, respectively. Concentrations were < 5 ng/mL with HPLC-MS/MS in 5 out of 10, 8 out of 10 and 7 out of 8 samples, respectively. DOAC remove ® corrected DOAC interference with dRVVT assays allowed excluding LA in 76, 85 and 95 % of the patients, respectively. without affecting dRVVT results in non-DOAC patients. Conclusion: For dRVVT testing in DOAC patients, we suggest the use of DOAC remove ® for every rivaroxaban sample, whereas it might only be used in positive apixaban and dabigatran samples. A residual DOAC interference cannot be ruled out in case of persisting dRVVT positive results after treatment with DOAC remove ®. For those with persisting positive results, LA-diagnosis using dRVVT remains questionable.

No abstract