Test shows risk for COVID-19 illness, death

A standard test that measures variation in the volume of red blood cells can identify hospitalized patients with COVID-19 who are at high risk for becoming critically ill and dying from the disease, according to research by a team of HMS investigators at Massachusetts General Hospital.

The findings are based on the team’s retrospective analysis of blood samples and medical records from more than 1,600 adults diagnosed with SARS-CoV-2 infection and admitted to a Boston-area hospital in March and April 2020.

The test, known as red blood cell distribution width, or RDW, is part of the complete blood count profile routinely used by physicians to screen, diagnose, and monitor a variety of conditions.

In the current study, the researchers found that variations in RDW above normal range indicated a higher mortality risk among those hospitalized for COVID-19. Patients who had RDW values above the normal range when they were admitted to the hospital had a mortality rate of 31 percent compared with a rate of 11 percent in patients with normal RDW values when admitted.

In addition, an increase in RDW after admission was linked with a heightened risk of dying, indicating that patients’ RDW could be tracked during hospitalization to help determine whether they are responding to treatment or getting worse. The link persisted even when the researchers accounted for the possible influence of other factors, including patient age, preexisting conditions, and variations in other laboratory findings.

Foy BH et al., JAMA Network Open, September 2020