Adapting heparin monitoring in response to COVID-19

ABSTRACT

At University Hospitals of Leicester NHS Trust (UHL), unfractionated heparin (UFH) has previously been monitored using activated partial thromboplastin time (aPTT) measurements in line with international practice. Prior to the COVID-19 pandemic, heparin assays using Anti-Xa methodology were used to monitor heparin activity in selected cases following approval by a haematologist. These tests were performed in the specialist haematology laboratory by specifically trained staff. Patients diagnosed with COVID-19 have a complex coagulopathy, leading to both prolongation and shortening of aPTT and reduced reliability in heparin monitoring compared with Anti-Xa assays ( Adie & Farina, 2021;Hardy et al., 2020 ). 1,2 In response to the pandemic, to ensure reliable monitoring of treatment, UHL transitioned from using aPTT monitoring to Anti-Xa assay testing. To enable Anti-Xa assay testing in the routine fast track laboratory a new operational procedure with a simplified assay needed to be validated;the initial work had commenced in January 2020 in response to clinician request. Verification of the modified sample centrifugation procedure and a hybrid Anti-Xa assay for UFH and low molecular weight heparin (LMWH) was completed in June 2020. New protocols and staff training in the fast track laboratory took place and the transition was completed in December 2020. To compare the effect this change had at UHL, and the laboratory's ability to adapt, Anti-Xa assay request data were compared between 2018 and 2020 over a 3-month period (October-December ). The findings are presented in Table 1. The study found a 12 times increase in Anti-Xa requests in 2020. The majority of these were for patients receiving extracorporeal membrane oxygenation (ECMO) requiring UFH from our specialist centre located at Glenfield Hospital;these patients required regular monitoring and repeated Anti-Xa assays. We also found a significant increase in requests to monitor prophylactic/intermediate dose heparin treatment in 2020, again with a significant number of these patients receiving ECMO, whereas in 2018 the majority of Anti-Xa assay requests were for treatment dose heparin monitoring. By transitioning from aPTT based to Anti-Xa based heparin monitoring available 24/7 in the fast track laboratory, patients had more reliable monitoring of their heparin activity . This has changed standard of care at UHL, which was of particular benefit to the patients on ECMO and continuous heparin monitoring. Due to the fact that part of the planning and verification work occurred prior to the COVID-19 pandemic the transition of this assay was completed reasonably quickly when the clinical need for this assay to be available on a 24/7 basis became urgent. We will continue to monitor data on therapeutic impact and bleeding episodes..