Microfluidic Point-Of-Care Ecarin Based Assays for Monitoring Direct Thrombin Inhibitor Therapy

Abstract

Direct thrombin inhibitors (DTIs), such as dabigatran, have maintained steady outpatient use due to their high oral bioavailability and relatively safe “on-therapy” range. The creation of new intravenous antibody reversal agents, like Idarucizumab, have renewed DTI monitoring interests. Current clinical methods within the United States lack the capacity to quantify DTI concentrations across wide ranges. At present, the international gold standard in quantifying DTI therapeutic thresholds is the ecarin clotting time (ECT). The linear prolongation of the ECT is directly proportional to specific DTI concentrations and inversely proportional to absorbance. This work focused on the development of a microfluidic paper analytic device (µPAD) that can quantify DTI concentration within a patient’s whole blood sample. Capillary action propels a small blood sample to flow through the nitrocellulose paper channels. Digital images of sample migration are then automatically captured by our self-coded Raspberry Pi and/or the Samsung Galaxy S8 smartphone camera. Commercial wax printers were used to create these disposable low-cost µPAD chips. Both the flow length and the blue absorbance from the plasma front on the μPAD were measured, allowing simultaneous, dual assay of ecarin clotting test (ECT) and ecarin chromogenic assay (ECA). Statistically significant (p < 0.05) changes in flow and absorbance were observed within our translational research study. Currently there are no quantitative commercially available point of care (POC) tests for the ECT within the U.S. Implementation of the ECT will differentiate between true supratherapeutic incidents and limit the unwarranted use of reversal agents. Additionally, DTIs have proved useful in maintaining anticoagulation during mechanical circulatory support in heparin induced cytopenia (HIT) patients. Our hopes are that our device will provide caregivers and patients the tools to monitor DTI therapy within both in and/or outpatient settings.