Another challenging question from Pam Owens at TriCore Reference Laboratories, Albuquerque: We have a patient on Dabigatran (Pradaxa) for multiple deep venous thromboses (DVTs) while on warfarin. While the results of his lupus-like inhibitor (LLI, lupus anticoagulant, LAC) testing do not look as wild as someone on argatroban, we did get a positive result on the DRVVT (ratio 1.27 with a cutoff of 1.18). Can dabigatran give us a false positive on DRVVT? We know it can on hexagonal phase phospholipid. We’re not even going to touch the protein C and S by clotting assay.
Dean Willett, Director of Marketing at Precision BioLogic responded that we haven’t done any studies with respect to patients on Dabigatran (or any other DTIs) but I think it’s safe to assume that there might be some interference with many clot-based assays.
George remarks that here is another (perhaps off-label) application of Dabigatran: a substitute for warfarin therapy when warfarin is ineffective. Dean and George would agree that any clot-based assay is likely to be prolonged by a direct thrombin inhibitor. With the ever-increasing use of the new oral DTI, we will continue to see issues like this.