Patients hospitalised with COVID-19 who have a high estimated blood viscosity are more likely to die from complications. High blood viscosity reduces blood flow to small vessels and raises the risk of blood clots. This blood thickness measurement can be used to predict mortality.

This study was published in the Journal of the American College of Cardiology.This is the first large-scale study to look at blood viscosity as a predictor of mortality in COVID-19 patients. When compared to common measures of inflammation and the blood clotting biomarker D-dimer, a simple calculation of blood viscosity was more robust in identifying hospitalised patients at risk of dying from COVID-19 complications. Acute phase reactants (fibrinogen, macroglobulins) that have been linked to acute COVID-19 infections raise blood viscosity.

Blood viscosity is a combined measure of these acute phase reactants as well as the cellular components that can increase during infection. When blood viscosity is high, physicians may consider therapeutic heparin, hydration, or glucocorticoid intensification to lessen the severity of the acute phase response to COVID-19.