- Doctors in Boston think they found another potential predictor that is associated with a higher risk of severe cases or even death from COVID-19 complications.
- Researchers have observed that COVID-19 patients who have higher RDW counts are at increased risk of death compared with patients who do not show elevated values.
- RDW is a standard component of routine blood tests, so it would be an accessible predictor of severe coronavirus cases if these findings are confirmed.
The novel coronavirus pandemic will cross a grim milestone by the time the weekend is over: 1 million people will have died of COVID-19 complications worldwide, more than one-fifth of which in the US alone. That’s out of about 7.5 million cases in the US and almost 33 million confirmed cases worldwide. The real number of people who contracted the illness since late December is significantly larger than that. Plenty of people survived the coronavirus without having been tested, just as some have likely died of COVID-19 without being diagnosed. In other words, the fatality rate (deaths out of total confirmed cases) hovers around 3%, and the real fatality rate (deaths out of all COVID-19 cases) is probably lower than that. That’s both good and bad news. Most people who are infected will survive, although “Long COVID” and MIS-C are secondary coronavirus worries affecting some patients and even children. But because the infection rate remains high and the virus spreads faster and more efficiently than other pathogens, the death toll is still significant.
There’s currently no treatment that can prevent deaths, although several drugs including remdesivir, dexamethasone, and blood thinners can help reduce complications. Several others are in testing, including monoclonal antibody drugs that might cure COVID-19 and even help prevent infections. Also, the goal of vaccination campaigns isn’t just to prevent infections, but also to reduce the severity of COVID-19 if infection occurs. Aside from finding a treatment that can prevent most deaths, doctors are also looking at early warning systems that might indicate which COVID-19 patients are more likely to develop severe complications. And a team of doctors from Massachusetts General Hospital thinks that a routine blood test can predict COVID-19 mortality.
The chances are that you’ve had your red blood cell distribution width (RDW) measured during any routine checkups where bloodwork was required. You probably haven’t paid any attention to it, and there’s no reason to, as long as values are normal. Your doctor might not even address this particular component of a regular blood test.
RDW measures the variation of red blood cell volumes, which can vary from cell to cell and for the same cell during its lifetime. The researchers speculate that “an elevated RDW in some circumstances may reflect a clinical state in which [red blood cell] production and turnover have slowed in the setting of increased production and turnover of leukocytes or platelets such as would occur in inflammation.”
But the researchers from Boston discovered that RDW might be an early predictor of a potentially fatal case of COVID-19. Published in the journal JAMA Network Open, their paper explains that an elevated RDW at the time of hospital admission and increased RDW during hospitalization were associated with increased mortality.
Patients with elevated RDW at admission were 6.12% more likely to die within 48 hours than patients with a normal RDW. A value greater than 14.5% at the time of admission was associated with an increase in mortality risk from 11% to 31%, the researchers concluded. They studied a cohort of 1,641 patients who were treated for COVID-19.
Even when adjusted for other factors including age, race, ethnicity, D-dimer level, absolute lymphocyte count, other blood count measures, and significant comorbidities, the risk of death remained high for patients with increased RDW numbers. D-dimers and lymphocytes have also been described as potential markers for severe COVID-19. Elevated RDW increased the risk of mortality in patients younger than 70 years compared to older groups.
The researchers point out that elevated RDW can also be associated with increased risk for a variety of other medical conditions, not just COVID-19: “Heart disease, pulmonary disease, sepsis, influenza, and cancer; complications associated with heart failure, severity of coronary artery disease and viral hepatitis, advanced stage and grade for many cancers; and the development of diabetes, chronic obstructive pulmonary disease, stroke, anemia, and many other conditions.”
But the correlation between high RDW counts and severe COVID-19 cases might prove to be important for the future management of the illness. Hospitals may develop new protocols that prioritize RDW screening to identify patients at risk of experiencing complications. The fact that RDW is a routine bloodwork test should also help with these plans.
More research is required to verify the findings. It’s unclear why RDW values change in people who have the disease, and the researchers could not tell what the baseline values were for those patients who died of COVID-19 complications after developing a high RDW count at admission. Patients suffering from other chronic illnesses that could be risk factors in COVID-19 could also have higher RDW values regardless of the coronavirus infection. Also, the study does not explain how soon RDW levels begin to increase after the onset of symptoms.