Hematologic manifestations of COVID-19

While SARS-CoV-2 causes frequent and potentially severe pulmonary disease, extrapulmonary manifestations may be a prominent part of the clinical spectrum, according to a review published in Nature Medicine.

Dr. Alan P. Lyss

In this comprehensive literature review, Aakriti Gupta, MD, of New York-Presbyterian/Columbia University Irving Medical Center and colleagues detailed the epidemiologic and clinical multisystem effects of COVID-19. The authors explained what is known and/or suspected about the pathophysiology of those effects and outlined the resultant management considerations.

Key mechanisms for multiorgan injury include direct viral toxicity, endothelial cell damage with inflammatory mediation of thrombosis, aberrant immune response, and dysregulation of the renin-angiotensin-aldosterone system.

The relative importance of each pathway in the clinical presentation of COVID-19 and the mechanism for extrapulmonary spread of SARS-CoV-2 infection are imperfectly understood, Dr. Gupta and colleagues noted.

As for the hematologic effects of COVID-19, patients may present with several laboratory abnormalities, but the most clinically relevant complications are thromboembolic.

COVID-19-associated coagulopathy

Dr. Gupta and colleagues noted that COVID-19–associated coagulopathy (CAC) is accompanied by elevated levels of D-dimer and fibrinogen, with minor abnormalities in prothrombin time, activated partial thromboplastin time, and platelet counts in the initial stage of infection.

Elevated D-dimer levels have been reported in up to 46% of hospitalized patients, and a longitudinal increase while hospitalized is associated with higher mortality.

In initial reports from China and the Netherlands, thrombotic complications were seen in up to 30% of COVID-19 patients in ICUs. Thromboembolic events have been reported in 17%-22% of critically ill COVID-19 patients in studies from Italy and France.

Globally, in severely affected COVID-19 patients, there have been reports of thromboses in intravenous catheters and extracorporeal circuits as well as arterial vascular occlusive events, including myocardial infarction, acute limb ischemia, and stroke.

There have been multiple small studies in which critically ill COVID-19 patients were routinely screened for thrombotic disease. In these studies, rates of thrombotic complications ranged from 69% to 85%, despite thromboprophylaxis. Variability in prophylactic and screening protocols explain discrepancies in event rates.

Pathophysiology

The abnormally high blood levels of D-dimer and fibrinogen during the early stages of SARS-CoV-2 infection are reflective of excessive inflammation rather than overt disseminated intravascular coagulation (DIC), which may develop in later stages of illness, according to Dr. Gupta and colleagues. The authors theorized that uninhibited inflammation, along with hypoxia and direct viral-mediated cellular injury, contribute to thrombotic complications in COVID-19 patients.

“The increased expression of ACE2 in endothelial cells after infection with SARS-CoV-2 may perpetuate a vicious cycle of endothelialitis that promotes thromboinflammation,” the authors wrote. “Collectively, hemostatic and inflammatory changes, which reflect endothelial damage and activation as well as critical illness, constitute a prothrombotic milieu.”

The authors noted that small autopsy series have shown high rates of microvascular and macrovascular thromboses, particularly in the pulmonary circulation, in COVID-19 patients.

Management considerations

Dr. Gupta and colleagues referenced interim guidelines from the International Society of Thrombosis and Haemostasis that recommend serial complete blood counts, with white blood cell differential and assessment of D-dimer, prothrombin time, and fibrinogen for hospitalized patients with COVID-19. The authors also cited guidelines published in the Journal of the American College of Cardiology that recommend routine risk assessment for venous thromboembolism in all hospitalized patients with COVID-19 and the consideration of standard-dose pharmaco-prophylaxis in patients who lack absolute contraindications.

Empiric use of higher-than-routine prophylactic-dose or therapeutic-dose anticoagulation in ICU patients in the absence of proven thromboses has been implemented in some institutions, Dr. Gupta and colleagues noted. Parenteral anticoagulants (such as low-molecular-weight or unfractionated heparin) are preferred to oral anticoagulants because of short half-life, available reversal agents, and the potential for drug interactions between oral agents and antiviral and/or antibacterial treatment, according to the authors.

They wrote that randomized clinical trials “will be crucial to establishing effective and safe strategies” for anticoagulation in COVID-19 patients. To this point, few randomized trials have been published to guide management of COVID-19–associated extrapulmonary manifestations, including CAC.

Research priorities

A more complete understanding of the organ-specific pathophysiology of this multisystem disease is vital, according to Dr. Gupta and colleagues.

“Regional, national, and international collaborations of clinicians and scientists focused on high-quality, transparent, ethical, and evidence-based research practices would help propel the global community toward achieving success against this pandemic,” the authors wrote.

They noted that common definitions and data standards for research are key for cross-institutional and international collaborations.

Initial attention to high-quality prospective scientific documentation standards would have been valuable and will be required for dedicated trials to address the multisystem effects of COVID-19.

Community of learners

As much as at any prior time in their careers, during the COVID-19 pandemic, health care providers have been enveloped in a community of learners – a group of people who share values and beliefs and who actively engage in learning from one another.

Through a patchwork of sources – news media, social media, traditional medical journals, general and COVID-focused meetings, and, most importantly, patients – we have been living in a learning-centered environment. Academicians, clinicians, practicing physicians, researchers, patients, family members, and caregivers have been actively and intentionally building a knowledge base together.

Through their published review, Dr. Gupta and colleagues have contributed meaningfully to the understanding our learning community has of the various extrapulmonary manifestations of COVID-19. The authors have provided a nice template for further research and clinical advances.

Dr. Gupta and colleagues disclosed financial relationships with a range of pharmaceutical companies and other organizations.

Dr. Lyss was a community-based medical oncologist and clinical researcher for more than 35 years before his recent retirement. His clinical and research interests were focused on breast and lung cancers as well as expanding clinical trial access to medically underserved populations. He is based in St. Louis. He has no conflicts of interest.

Source: Gupta A et al. Nat Med. 2020 Jul;26(7):1017-32.