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Hello, welcome to Clot Chronicles. My name is Margaret Fang, and I am Professor of Medicine here at the University of California San Francisco where I practice as a hospitalist physician and serve as the Medical Director of the Anticoagulation Clinic. On today’s episode of Clot Chronicles, I’m going to be reviewing the main findings from our study that quantify the risk of venous thromboembolism (VTE) in patients who are hospitalized with COVID-19.
First, let me provide some background. In the early days of the pandemic, we saw a number of reports of extraordinarily high rates of VTE in patients who were hospitalized with COVID-19. Some of these early studies described rates of 20 or even 30%, but these studies had limitations. COVID was a very new disease at the time, the studies were small, and they lacked control groups – plus some hospitals aggressively screened patients for VTE.
So, we were left with the question what is the actual risk of VTE associated with COVID-19? In order to answer this question, our research group conducted an observational study to answer these questions:
- Does COVID raise your risk for thrombosis, and if so, by how much?
- And finally, are there patient-level factors that would make one particularly susceptible to VTE?
The study patients were adults enrolled in the 36 hospitals, part of Kaiser Permanente Northern California and Kaiser Permanente Southern California, two healthcare systems with integrated hospital and ambulatory care. What we did was first identify all patients hospitalized with COVID. And then we matched these COVID-positive patients to an equivalent set of control patients who were hospitalized for non-COVID reasons. Our goal was to create very similar comparison groups whose main difference was the presence of COVID infection.
In particular, we matched patients based on their month of admission and their LAPS2 score. This is a validated and accurate way of predicting someone’s risk of short-term mortality during hospitalization. Once we had these matched groups, we then searched the entire health systems’ databases to determine which patients developed VTE within 30 days of their hospital admission.
So, what did we find? First, we were able to effectively match 6,319 patients hospitalized with COVID to 6,319 without COVID, who were, on average, 60 years old, 45.9% of whom were women, and 53.1% of self-reported Hispanic ethnicity. Within these two groups, we then compared their outcomes. You can see that patients with COVID had a much higher in-hospital death rate than those without COVID. In fact, 13% of patients with COVID died in the hospital compared to only 2.9% in people without COVID.
We then looked at VTE outcomes within 30 days and 160 patients with COVID were diagnosed with VTE compared to 153 patients without COVID. Now you might think these numbers don’t look that different – but remember patients with COVID were much more likely to die and so they wouldn’t have developed VTE. So, if you account for this higher competing risk of death with COVID, we find that the risk of VTE is 3.5 times higher in patients who have COVID.
Let me also point out that this was despite COVID patients being much more likely to get pharmacologic VTE prophylaxis while in the hospital. Several patient-level factors were also linked to a higher VTE risk in COVID, including older age, a past history of VTE, and higher body mass index.
So, the bottom line of our study is, yes, hospitalized patients with COVID-19 do, indeed, have a higher risk of developing a deep vein thrombosis (DVT) or pulmonary embolism (PE), and this risk is more than three times the risk of comparably sick patients who don’t have COVID. This reinforces to clinicians that we should be particularly vigilant for thrombosis in patients with COVID-19.
Our study also highlights the importance of continuing studies on the usefulness of different anticoagulant strategies in people who have COVID. Clinical trials are, in fact, finding that therapeutic anticoagulation can be beneficial in some hospitalized patients with COVID but not for others.
Thank you so much for joining us today on this episode of Clot Chronicles.