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?:abstract
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Keywords: COVID-19, Hypercoagulability, Thromboembolism, Coagulation The 2019 novel coronavirus (COVID-19) pandemic has spread rapidly, infecting millions of people in a matter of months 1 While COVID-19 is commonly linked to severe pneumonia often progressing to acute respiratory distress syndrome (ARDS), a new feature of the disease has come to light 2 A remarkably high number of COVID-19 patients are presenting with a deranged coagulation profile resulting in a hypercoagulable state 1-10 The coagulation defect noted in this population has been linked to an increased risk of thrombotic complications as well as poor prognosis 2,4,6,7 Proposed mechanisms behind the coagulopathy include severe inflammation, hypoxia, immobilization, and diffuse intravascular coagulation (DIC) In a study from China by Tang et al , coagulation tests were retrospectively reviewed in 183 consecutive patients infected with COVID-19 4 Findings revealed that non-survivors of the disease had significantly higher D-dimer, fibrin degradation products (FDPs), and longer prothrombin times (PT) compared to those of survivors on admission 4 The authors state that the use of these conventional coagulation tests may be beneficial in guiding treatment and that they may be directly related to patient prognosis 4 Additional findings included significantly lower fibrinogen and antithrombin (AT) levels during late hospitalization 4 It was also noted that 71 4% of non-survivors met criteria for overt disseminated intravascular coagulation (DIC), making it a common feature of severe disease in this cohort 4 Physicians at a hospital in Milan, Italy observed a number of patients developing deep vein thromboses (DVTs) and pulmonary embolisms (PEs), while lacking the presence of DIC as described by Tang et al 4,6 Panigada et al decided to create their own study utilizing a thromboelastography (TEG) point of care device as well as conventional coagulation testing 6 The study included 24 intubated COVID-19 patients who were randomly selected from those admitted to the intensive care unit (ICU) 6 Collective TEG results revealed a significant state of hypercoagulability, which may provide explanation for the frequency of DVTs and PEs seen within their facility Thromboelastometry profiles were similar to those observed by Panigada et al , as faster clot formation times and higher maximum clot firmness seen were consistent with a hypercoagulable state 6,7 Spieza et al mentions 23% of the patients in the study developed DVTs, even while being treated with prophylactic anticoagulation 7 While neither of these studies support the notion of consumption coagulopathy as described by Tang et al , they do share the finding of markedly high D-dimer levels, supporting the conclusion that elevated D-dimer is an independent risk factor for severe disease 4,6,7 The hypercoagulability described in both reports may also support the use of antithrombotic drugs in this population as a method to prevent thromboembolic complications 6,7 Han et al sought to evaluate the differences among blood coagulation parameters between COVID-19 patients and healthy controls in order to provide insight into their ability to predict progression of the disease 10 The study involved 94 patients from a Wuhan China hospital with positive COVID-19 diagnosis and 40 healthy patients for the control group 10 Compared to the control group, COVID-19 patients presented with significantly lower AT values and significantly higher FDP and D-dimer values 10 After confirming findings from previous studies, the cohort of COVID-19 positive patients was split into three groups classified as ordinary, severe, or critical states of disease 4,6,7,10 D-dimer and FDP values were found to be significantly higher in the severe disease group when compared to the mild disease group 10 This finding highlights potential benefits of D-dimer and FDP monitoring in predicting the progression of COVID-19 disease 10 Fogarty et al considers how ethnicity plays a significant role in coagulation, and that Chinese are 3-4 times less likely to experience venous thromboembolism (VTE) when compared to Caucasians 2 In fact, VTE prophylaxis is far less prevalent in China for this reason 2 Researchers designed a study to determine whether coagulopathic features differ between Chinese and Caucasian patients 2 The cohort consisted of 83 COVID-19 positive patients recruited from St James Hospital in Dublin, Ireland Eighty-one percent of patients were Caucasian, 12% Asian, and 6% African 2 Blood tests were performed on admission revealing significantly increased D-dimer, fibrinogen, and C-reactive protein levels 2 The cohort was next divided into two groups based on patients who were discharged and those requiring ICU admission 2 D-dimer, CRP, and fibrinogen levels on admission were found to be significantly higher in the groups requiring ICU level care 2 Unlike Tang et al , DIC was not identified within the cohort and platelet levels remained within a normal range 4,2 The lack of DIC development is hypothesized to be related to the use of pharmacologic thromboprophylaxis, which was utilized in all patients within this cohort 10 Significant hypercoagulability related to severity of disease was, however, similar to that seen in Chinese cohorts 2,4,10 Incidence of Thromboembolism The hypercoagulable state described in previous studies has been found to leave patients with COVID-19 infections at increased risk for thromboembolism
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