Coronavirus disease 2019 (COVID-19) is a viral illness caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), currently causing a pandemic affecting many countries around the world, beginning in December 2019 and spreading rapidly on a global scale since. Globally, its burden has been increasing rapidly, with more than 1.2 million people testing positive for the illness and 123,000 people losing their lives, as per April 15th’s WHO COVID-19 Situation Report.1 These numbers are increasing with each passing day. Clinically, SARS-CoV-2 has a highly variable course, ranging from mild disease manifested as a self-limited illness (seen in younger and healthier patients) to severe pneumonia/ARDS and multiorgan failure with intravascular coagulopathy.2
In this article, we intend to investigate and establish a comprehensive review of COVID-19–associated coagulopathy mechanisms, laboratory findings, and current management guidelines put forth by various societies globally.
Mechanism of coagulopathy
COVID-19–associated coagulopathy has been shown to predispose to both arterial and venous thrombosis through excessive inflammation and hypoxia, leading to activation of the coagulation cascade and consumption of coagulation factors, resulting in microvascular thrombosis.3 Though the exact pathophysiology for the activation of this cascade is not known, the proposed mechanism has been: endothelial damage triggering platelet activation within the lung, leading to aggregation, thrombosis, and consumption of platelets in the lung.2,5,6
Fox et al. noted similar coagulopathy findings of four deceased COVID-19 patients. Autopsy results concluded that the dominant process was diffuse alveolar damage, notable CD4+ aggregates around thrombosed small vessels, significant associated hemorrhage, and thrombotic microangiopathy restricted to the lungs. The proposed mechanism was the activation of megakaryocytes, possibly native to the lung, with platelet aggregation, formation of platelet-rich clots, and fibrin deposition playing a major role.4
It has been noted that diabetic patients are at an increased risk of vascular events and hypercoagulability with COVID-19.7 COVID-19 can also cause livedo reticularis and acrocyanosis because of the microthrombosis in the cutaneous vasculature secondary to underlying coagulopathy, as reported in a case report of two U.S. patients with COVID-19.8
Clinical and laboratory abnormalities
A recent study reported from Netherlands by Klok et al. analyzed 184 ICU patients with COVID-19 pneumonia and concluded that the cumulative incidence of acute pulmonary embolism (PE), deep vein thrombosis (DVT), ischemic stroke, MI, or systemic arterial embolism was 31% (95% confidence interval, 20%-41%). PE was the most frequent thrombotic complication and was noted in 81% of patients. Coagulopathy, defined as spontaneous prolongation of prothrombin time (PT) > 3s or activated partial thromboplastin time (aPTT) > 5s, was reported as an independent predictor of thrombotic complications.3
Hematologic abnormalities that were noted in COVID-19 coagulopathy include: decreased platelet counts, decreased fibrinogen levels, elevated PT/INR, elevated partial thromboplastin time (PTT), and elevated d-dimer.9,10 In a retrospective analysis9 by Tang et al., 71.4% of nonsurvivors and 0.6% of survivors had met the criteria of disseminated intravascular coagulation (DIC) during their hospital stay. Nonsurvivors of COVID-19 had statistically significant elevation of d-dimer levels, FDP levels, PT, and aPTT, when compared to survivors (P < .05). The overall mortality in this study was reported as 11.5%.9 In addition, elevated d-dimer, fibrin and fibrinogen degradation product (FDP) levels and longer PT and aPTT were associated with poor prognosis.
Thus, d-dimer, PT, and platelet count should be measured in all patients who present with COVID-19 infection. We can also suggest that in patients with markedly elevated d-dimer (three- to fourfold increase), admission to hospital should be considered even in the absence of severe clinical symptoms.11