Blood test determining red blood cell distribution width can depict who is at risk of severe COVID-19

The total number of confirmed cases of COVID-19 infection have crossed the mark of 32 million across the globe, while the number of deaths is nearing one million. The deaths have been more prevalent in the elderly population and those with comorbidities. Previous studies have shown that the reasons behind these deaths can be a cytokine storm (excess inflammatory cells in the body), increased levels of D-dimers and low white blood cell count.

Increased D-dimer levels were seen to be associated with high mortality rates as it stimulated cytokine storms, abnormal blood clotting and organ failure.

In recent research, published in the journal JAMA Network on 23rd September 2020, it was found that high red blood cell distribution width (RDW) in the blood of a COVID-19 patient can also increase their risk of mortality.

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The link between RDW and COVID-19

Red blood cell distribution width (RDW) is a test done by taking the blood sample of a person in order to measure the size and volume of red blood cells.

Scientists from the Harvard Medical School conducted a study on 1,641 patients, of mean age 62 years, who were diagnosed with COVID-19 and were admitted between 4th March 2020 and 28th April 2020 to one of the following hospitals - Massachusetts General Hospital, Brigham and Women’s Hospital, North Shore Medical Center and Newton-Wellesley Hospital.

The scientists examined the RDW, white blood cell count and D-dimer levels of all these patients on a daily basis along with standard clinical care.

The results 

The results of the study showed that COVID-19 positive patients who presented with RDW greater than 14.5 percent during admission had a mortality risk of 31 percent. However, patients who had an RDW of 14.5 percent or less had a mortality risk of 11 percent.

The relative risk of mortality for the patients who had an increased RDW compared to those who had a low RDW was 2.73 times. It was also found that high levels of RDW increased the mortality risk in people younger than 50 years as well as in those above the age of 80 years.

The scientists further found that the relative risk of death (between those with low and high RDW) increased within 48 hours of admission. Within 48 hours of admission, the mortality risk of patients with a normal RDW of 14.5 percent or less increased by 0.8 percent, whereas, for those with an RDW greater than 14.5 percent, the mortality risk increased by 4.9 percent.

The conclusion

The scientists stated that an increased RDW in COVID-19 patients at the time of hospital admission or during hospitalization can increase their mortality risk.

The scientists further found that an elevated RDW during hospitalization can increase the mortality risk by 6 percent to 24 percent for those who had normal RDW during admission and 22 percent to 40 percent for those who had an elevated RDW during admission.

With this study, the scientists concluded that COVID-19 patients with high RDW during hospital admission are at a 6.12 times higher risk of dying within 48 hours than those with a normal RDW.

For more information, read our article on Blood Test (CBC).

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