More on COVID‐19 coagulopathy in Caucasian patients

We are grateful for the comments of Marrietta et al.1 and welcome the opportunity to provide further details on the coagulopathy observed in our patients with coronavirus disease 2019 (COVID‐19) infection.2 The weight‐adjusted low‐molecular‐weight heparin (LMWH) thromboprophylaxis used in the study is that routinely used for hospital in‐patients in our institution, consistent with national recommendations.3, 4 With respect to the cohort of patients with COVID‐19 enrolled in our study, it is important to highlight that 74% of patients received enoxaparin 40 mg (4000 iu) subcutaneously once daily. In 12% of patients, the dose of enoxaparin was reduced to 20 mg once daily due to a weight of < 50 kg (8%) or renal impairment (4%). In all, 11% of our cohort were already on extended‐duration therapeutic anticoagulation at time of presentation with COVID‐19 for a variety of reasons (including atrial fibrillation, mitral valve replacement, and cancer‐associated venous thromboembolism) and consequently were maintained on the same during their admissions. Finally, 2% of patients did not receive thromboprophylaxis due to perceived increased bleeding risks. Of particular importance in respect to the point raised by Marrietta et al.1, only one patient with COVID‐19 actually received an enoxaparin dose of > 40 mg for thromboprophylaxis (due to increased body weight of > 100 kg). In summary therefore, the doses of LWMH used in our cohort are entirely consistent with best practice guidelines. In addition, none of our cohort developed any major bleeding or clinically relevant non‐major bleeding complications.5, 6<br

COVID-19 coagulopathy in Caucasian patients

Although the pathophysiology underlying severe COVID19 remains poorly understood, accumulating data suggest that a lung-centric coagulopathy may play an important role. Elevated D-dimer levels which correlated inversely with overall survival were recently reported in Chinese cohort studies. Critically however, ethnicity has major effects on thrombotic risk, with a 3–4-fold lower risk in Chinese compared to Caucasians and a significantly higher risk in African-Americans. In this study, we investigated COVID19 coagulopathy in Caucasian patients. Our findings confirm that severe COVID19 infection is associated with a significant coagulopathy that correlates with disease severity. Importantly however, Caucasian COVID19 patients on low molecular weight heparin thromboprophylaxis rarely develop overt disseminated intravascular coagulation (DIC). In rare COVID19 cases where DIC does develop, it tends to be restricted to late-stage disease. Collectively, these data suggest that the diffuse bilateral pulmonary inflammation observed in COVID19 is associated with a novel pulmonary-specific vasculopathy termed pulmonary intravascular coagulopathy (PIC) as distinct to DIC. Given that thrombotic risk is significantly impacted by race, coupled with the accumulating evidence that coagulopathy is important in COVID19 pathogenesis, our findings raise the intriguing possibility that pulmonary vasculopathy may contribute to the unexplained differences that are beginning to emerge highlighting racial susceptibility to COVID19 mortality