Background
Direct oral anticoagulants (DOACs) interfere with lupus anticoagulant (LAC) testing. DOAC‐Stop (D‐S) represents a preanalytical strategy to cope with this issue.
Objectives
To assess D‐S’s ability to remove DOACs from plasma and overcome DOAC interference in LAC assays and to evaluate D‐S’s applicability in a representative patient cohort with routine LAC request.
Methods
Apixaban (30‐933 ng/mL), edoxaban (31‐1060 ng/mL), rivaroxaban (35‐1020 ng/mL), and dabigatran (20‐360 ng/mL) were spiked to normal plasma. Aliquots were treated with D‐S or untreated before DOAC and LAC testing. Patient samples containing DOAC (n = 43), vitamin K antagonists (n = 25), heparins (n = 21), or no anticoagulants (n = 63) were tested for LAC before and after D‐S.
Results
Spiking experiments revealed false‐positive LAC from low concentrations of DOACs except for apixaban. Following D‐S, DOAC levels were below lower limits of quantification, except for apixaban at the highest concentration, and no false‐positive LAC was obtained. DOAC levels were below lower limits of quantification after D‐S in 39/43 DOAC‐containing patient samples. For 23/29 LAC‐positive DOAC‐containing samples, LAC tests became negative after D‐S, whereas 3/6 samples remaining positive were from patients with (high probability for) antiphospholipid syndrome. In the non‐DOAC‐treated groups, LAC changed from positive to negative in 10 and vice versa in 2 cases.
Conclusions
D‐S limits DOAC interference in LAC assays. DOAC concentration measurement should be performed in D‐S treated samples because incomplete removal may occur. Applying D‐S to vitamin K antagonist‐containing, heparin‐containing, or not‐anticoagulated samples may lead to erroneous LAC results. Therefore, D‐S should only be used in plasma from DOAC‐treated patients.