Dr. O’Donnell and colleagues noted that most studies of COVID-19-associated coagulopathy published to date have been with Chinese patients.
“This is important because race and ethnicity have major effects upon thrombotic risk. In particular, epidemiological studies have shown that the incidence of venous thromboembolism (VTE) is approximately three to fourfold lower in Chinese compared to Caucasian individuals. Conversely, VTE risk is significantly higher in African-Americans compared to Caucasians,” they wrote.
Because of the lower risk of VTE in the Chinese population, thromboprophylaxis with low-molecular-weight heparin (LMWH) or other agents is less frequently used in Chinese hospitals than in hospitals with predominantly non-Asian patients, they noted.
To see whether the were differences in coagulopathy between Chinese and white patients, the researchers enrolled 55 men and 28 women, median age 64, who were admitted to St. James Hospital with COVID-19 infections from March 13 through April 10, 2020. The cohort included 67 patients of white background, 10 of Asian ancestry, 5 of African ethnicity, and 1 of Latino/Hispanic ancestry.
Of the 83 patients, 67 had comorbidities at admission. At the time of the report, 50 patients had fully recovered and were discharged, 20 remained in the hospital, and 13 had died. In all, 50 patients were discharged without needing ICU care, 23 were admitted to the ICU, and 10 required ICU but were deemed “clinically unsuitable” for ICU admission.
Although the patients had normal prothrombin time (PT) and normal activated partial thromboplastin time (APTT), plasma d-dimer levels were significantly elevated and were above the range of normal in two-thirds of patients on admission.
Despite the increased d-dimer levels, however, there was no evidence of DIC as defined by the International Society of Thrombosis and Hemostasis Scientific and Standardization committee (ISTH SSC) guidelines. Platelet counts were in the normal range in 83.1% of patients, and only five had counts less than 100 x 109/L at admission. Fibrinogen levels were also elevated, as were C-reactive protein levels, both likely indicating an acute phase response.
“Thus, despite the fact that thrombotic risk is much higher in Caucasian patients and the significant elevated levels of d-dimers observed, overt DIC as defined according to the ISTH SSC DIC score was present in none of our COVID-19 patients at time of admission. Nevertheless, our data confirm that severe COVID-19 infection is associated with a significant coagulopathy in Caucasian patients that appears to be similar in magnitude to that previously reported in the original Chinese cohorts,” they wrote.
When they compared patients who required ICU admission for ventilator support and those who died with patients who were discharged without needing ICU support, they found that survivors were younger (median age 60.2 vs. 75.2 years), and that more critically ill patients were more likely to have comorbidities.
They also found that patients with abnormal coagulation parameters on admission were significantly more likely to have poor prognosis (P = .018), and that patients in the adverse outcomes group had significantly higher fibrinogen and CRP levels (P = .045 and .0005, respectively).
There was no significant difference in PT between the prognosis groups at admission, but by day 4 and beyond PT was a median of 13.1 vs. 12.5 seconds in the favorable outcomes groups (P = .007), and patients with poor prognosis continued to have significantly higher d-dimer levels. (P = .003)
“Cumulatively, these data support the hypothesis that COVID-19–associated coagulopathy probably contributes to the underlying pulmonary pathogenesis,” the researchers wrote.
They noted that the angiotensin converting enzyme 2 (ACE-2) receptor that COVID-19 uses to enter cells is expressed on both type II pneumocytes and vascular endothelial cells within the lung, suggesting that the coagulopathy may be related to direct pulmonary endothelial cell infection , activation, and/or damage, and to the documented cytokine storm that can affect thrombin generation and fibrin deposition within the lungs.
“In the context of this lung-centric vasculopathy, we hypothesize that the refractory acute respiratory distress syndrome phenotype observed in severe COVID-19 is due to concurrent ‘double-hit’ pathologies targeting both ventilation (V) and perfusion (Q) within the lungs where alveoli and pulmonary microvasculature exist in close anatomical juxtaposition,” they wrote.
The investigators noted that larger randomized trials will be needed to determine whether more aggressive anti-coagulation and/or targeted anti-inflammatory therapies could effectively treated PIC in patients with severe COVID-19.
The study was supported by the Wellcome Trust and the Health Research Board Health Service and the Research and Development Division, Northern Ireland. Dr. O’Donnell disclosed speakers bureau activities, advisory board participation, and research grants from multiple companies. The other doctors had no relevant conflicts of interest to disclose.
SOURCE: Fogarty H et al. Br J Haematol. 2020 Apr 24. doi: 10.1111/bjh.16749.