How and when to measure anticoagulant effects of direct oral anticoagulants? Practical issues.

Direct oral anticoagulants (DOACs) do not require dose adjustment based on laboratory testing. However, it might be necessary to measure their plasma concentrations in the following specific situations: 1) before thrombolytic therapy in patients with stroke; 2) before surgery or invasive procedure; 3) in case of adverse events (thrombosis or hemorrhage); 4) when immediate reversal of anticoagulation is needed; 5) in patients with extreme body weight; 6) when administering additional drugs potentially interfering with DOACs; and 7) when overdosage is suspected regardless of concomitant bleeding. Basic coagulation tests, such as prothrombin and activated partial thromboplastin time, should not be used as standalone tests to assess the levels of anticoagulation as they are not specific for DOACs and their results are dependent on the type of reagent used for testing. Plasma DOAC concentrations should be assessed by dedicated tests: dilute thrombin time or ecarin tests (for dabigatran) or anti-factor Xa assays (for anti-factor Xa inhibitors). Dedicated tests should be calibrated against their respective plasma calibrators at certified DOAC concentrations and results should be expressed as ng/ml. Caution should be exerted when interpreting the results of the most common hemostatic parameters such as antithrombin, proteins C and S, lupus anticoagulant, or individual coagulation factors, as they may be strongly affected by the presence of a DOAC. Whenever possible, these parameters should be measured 4 to 5 days after discontinuation of DOAC anticoagulation.

Harmful and Beneficial Effects of Anticoagulants in Patients With Cirrhosis and Portal Vein Thrombosis.

BACKGROUND & AIMS: Vitamin K antagonists (VKAs) promote recanalization of portal vein thrombosis (PVT) in patients with cirrhosis. However, the benefit of PVT recanalization might be offset by major and minor bleeding associated with use of anticoagulants. We evaluated harmful and beneficial effects of VKA in patients with PVT and cirrhosis. METHODS: We performed a retrospective study of 63 consecutive patients with cirrhosis given anticoagulants for the first detection of non-neoplastic PVT from 2003 to 2015 in Italy. We collected data on bleeding events in these patients and compared them with those from patients without cirrhosis with venous thromboembolism (VTE) (n = 160) for up to 4 years. Time in the therapeutic range, based on the international normalized ratio, was used to determine the quality of anticoagulation. We also collected data from 139 patients with cirrhosis who did not receive VKAs (controls), to analyze portal hypertension-related events. We performed survival analyses to determine the effects of VKA in patients with PVT vs controls. RESULTS: The group with VTE and the group with PVT were comparable in age, sex, and time in the therapeutic range, but patients with VTE received VKAs for a longer time period (31.1 ± 16.9 mo vs 23.3 ± 16.2 mo; P = .002). The incidence of major or minor bleeding was higher in patients with PVT than patients with VTE (major, 24% vs 7%; P = .012; minor, 29% vs 19%; P = .024). Patients with PVT had a higher rate of major bleeding from the upper-gastrointestinal tract than patients with VTE (P = .019), but there were no significant differences in other types of major bleeding (P = .376). Patients with PVT and controls had the same rate of upper-gastrointestinal bleeding. Complete recanalization in patients with PVT receiving VKA (n = 31) was independently associated with increased portal hypertension-related event-free and transplantation-free survival times. CONCLUSIONS: In a retrospective analysis of 63 patients with cirrhosis given anticoagulants for PVT, we found VKA use to increase risk of minor bleeding, compared with patients without cirrhosis given VKA. However, this risk is offset by the ability of VKA to increase portal hypertension-related, event-free, and transplantation-free survival of patients with PVT recanalization. Portal hypertension, rather than anticoagulants, could account for the difference in risk of major bleeding between patients with PVT vs patients with VTE.