Associations between whole blood viscosity and SARS-CoV-2-linked death

In a recent study published in the Journal of the American College of Cardiology, researchers depicted the link between coronavirus disease 2019 (COVID-19)-associated mortality and whole blood viscosity (WBV).

Study: Association of Blood Viscosity With Mortality Among Patients Hospitalized With COVID-19. Image Credit: giggsy25/Shutterstock
Study: Association of Blood Viscosity With Mortality Among Patients Hospitalized With COVID-19. Image Credit: giggsy25/Shutterstock


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a betaCoV, is responsible for the ongoing COVID-19 pandemic. Unlike other betaCoVs, COVID-19 features hypercoagulability, which significantly raises the risk of mortality and morbidity.

Although SARS-CoV-2 infection was identified primarily as a respiratory condition, mounting evidence characterized COVID-19 by aberrant blood rheology, a dysregulated immune response, and thrombotic complications. A clinically verified indicator of blood rheology and a recognized determinant of cardiovascular risk is WBV.

According to existing reports on COVID-19 patients, WBV levels substantially heighten during the acute and recovery phases of the illness. Elevated plasma viscosity, a critical element of WBV, has also been linked to worse outcomes and thrombotic events in many studies involving acute COVID-19 patients.

About the study

The present multihospital retrospective cohort research aimed to ascertain the relationship between estimated BV (eBV) and death in hospital-admitted SARS-CoV-2 patients. The authors speculate that higher WBV was linked to death in hospitalized COVID-19 patients. They sought to explore the prognostic usefulness of eBV that could predict all-cause fatality across hospitalized COVID-19 patients.

The research volunteers included 5,621 hospital-admitted COVID-19 patients from the Mount Sinai Health System between 27 February 2020 and 27 November 2021. Further, eBV was determined utilizing the Walburn-Schneck model. To assess the correlation between eBV and death, multivariate Cox proportional hazards models were applied. Sex, age, race, metabolic and cardiovascular comorbidities, baseline inflammatory biomarkers, and in-house pharmacotherapy were all considered variables.


The authors discovered that heightened estimated low-shear BV (eLSBV) and estimated high-shear BV (eHSBV) were associated with elevated in-hospital death among 5,621 hospitalized acute COVID-19 patients.

The increase in mortality associated risk per 1-centipoise (cP) in eHSBV corresponded to a 36% higher death risk. Likewise, the risk of death increased by 7% with every 1-cP increase in eLSBV. Consistent relationships between high eBV and death were observed in all subsets of sex, age, metabolic or cardiovascular comorbidities, in-house pharmacotherapy (statins and heparins), and inflammatory laboratory marker levels.

In models that controlled for C-reactive protein (CRP), interleukin 6 (IL-6), D-dimer, and other biomarkers frequently used for risk classification of hospitalized COVID-19 patients, the team found that BV predicted mortality. Participants in the upper quartiles of eHSBV exhibited an adjusted hazard ratio (aHR) of 1.50 even after adjusting for the levels of IL-6 and CRP, which were linked to higher mortality.

The scientists did not find a similar correlation between WBV and COVID-19-linked mortality in the Asian population. With only 6% of COVID-19 patients hospitalized in the study coming from an Asian background, there may be a lack of enough occurrences to detect a statistical discrepancy. Furthermore, the researchers speculate that Asians may have innate defense pathways against the impact of blood hyperviscosity given that they had the lowest rate of thromboembolic disease.


The scientists claimed that the current research was the first multicenter, extensive study to examine the prognostic significance of WBV for predicting all-cause death among hospitalized COVID-19 patients. According to the authors, just one prior study, a longitudinal prospective population-based investigation, has looked into the relationship between WBV and death.

The study findings illustrated that among hospitalized SARS-CoV-2 patients, eHSBV and eLSBV were linked to higher in-hospital mortality rates. In the study, increased eLSBV and eHSBV were linked to an elevation in inpatient COVID-19 mortality. Nonetheless, after accounting for inflammatory biomarkers such as IL-6, the association between eLSBV and mortality was no longer statically relevant.

Likewise, high-shear viscosity was linked more closely to the death, with a 1-cP rise in eHSBV mirroring a 36% higher probability of mortality relative to eLSBV's 7%. The team noted that future research on the pathologic processes and variations of high- and low-shear blood hyperviscosity in the context of COVID-19 might be necessary.

Nevertheless, the connection between eBV and mortality persisted across different subgroups, particularly in patients without comorbid conditions. Besides, the authors emphasized the necessity of further studies examining the influence of racial disparities on the clinical outcomes of COVID-19.

Together, the current study depicted that higher mortality among hospitalized SARS-CoV-2 patients was correlated substantially with increased eBV. As a result, eBV could predict patient outcomes in COVID-19's early phases. The findings also highlighted the need to consider potential future treatments that aim to lower WBV.

Journal reference:
Shanet Susan Alex

Written by

Shanet Susan Alex

Shanet Susan Alex, a medical writer, based in Kerala, India, is a Doctor of Pharmacy graduate from Kerala University of Health Sciences. Her academic background is in clinical pharmacy and research, and she is passionate about medical writing. Shanet has published papers in the International Journal of Medical Science and Current Research (IJMSCR), the International Journal of Pharmacy (IJP), and the International Journal of Medical Science and Applied Research (IJMSAR). Apart from work, she enjoys listening to music and watching movies.


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