MGH study says routine blood test may predict COVID-19 hospital death risk

EMTs rush a patient into the emergency room at Massachusetts General Hospital in April. MGH researchers say a simple blood test could give doctors an early-warning signal of who is at higher risk of dying from the coronavirus.Stan Grossfeld/ Globe Staff

Massachusetts General Hospital researchers say they’ve found that a routine test of blood cells may provide a key clue to whether patients admitted to the hospital with the coronavirus face a higher risk of dying.

A standard test that quantifies the variation in the size of red blood cells, called red cell distribution width (RDW), was correlated with patient mortality, researchers said in a statement from the hospital. The results from the MGH Center for Systems Biology were published Wednesday in JAMA Network Open.

“We wanted to help find ways to identify high-risk COVID patients as early and as easily as possible: who is likely to become severely ill and may benefit from aggressive interventions, and which hospitalized patients are likely to get worse most quickly,” said Dr. John M. Higgins, senior author of the study and an investigator in the MGH pathology department, in the statement.

The study concluded that “RDW measured at admission and during hospitalization was associated with a statistically significant increase in mortality. RDW is a routine laboratory test that may be useful in risk stratification of hospitalized patients with COVID-19.”

Patients with RDW values above the normal range when they were admitted had a 2.7 times higher risk of dying, with a mortality rate of 31 percent compared with 11 percent in patients with normal RDW values, the hospital said. Increasing RDW levels during the hospital stay were also associated with a higher risk of dying.

Higgins said in a telephone interview that doctors admitting patients with COVID-19 to the hospital may look at a number of tests to determine how a COVID-19 patient will fare, but the study suggests that the RDW number could be a valuable addition to their toolkit.

“Our study shows this is a test that they ought be spending at least some time looking at,” he said.

He said a doctor admitting a COVID-19 patient who “looks OK but has an elevated RDW” should “take a second look, keep a close eye on that patient” because they have a “higher risk of progression to severe disease.”

“Many doctors probably already have this measure as part of tests that are routinely ordered for an admitted patient,” but they may not think of looking at it, he said. “We’ve shown in our study that this marker does add additional significant information.”

The study analyzed 1,641 patients 18 and older admitted to Massachusetts General Hospital, Brigham and Women’s Hospital, North Shore Medical Center, and Newton-Wellesley Hospital between March 4 and April 28.

The lead author of the paper was Brody Foy, a research fellow in systems biology at MGH and Harvard Medical School.