RDW Test Is Helpful for Prognostication in COVID-19
Key findings
- In previous research, red blood cell distribution width (RDW) has appeared to be a nonspecific marker of illness that can serve as a biomarker for patient risk stratification
- In this retrospective study of 1,641 patients, RDW greater than 14.5% at the time of hospital admission for COVID-19 was associated with an increase in mortality risk from 11% to 31%
- Risk of mortality associated with RDW remained statistically significant after adjustment for patient age, race, ethnicity, D-dimer level, absolute lymphocyte count, other blood count measures and five major comorbidities
- Patients whose RDW increased during admission also had increased mortality risk
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Red blood cell distribution width (RDW) is routinely measured as part of complete blood count tests. It represents the variation in red blood cell volume between cells and the typical decrease in each red blood cell's volume over its lifespan.
Previous studies have shown that in some illnesses, RDW elevation is caused by delayed clearance of older RBCs and a net decrease in red blood cell production. Elevated RDW has been associated with increased risk of mortality, development of certain chronic diseases, and disease complications and severity. There's also evidence that RDW is useful for risk stratification among patients diagnosed with the same acute illness.
Brody H. Foy, DPhil, research fellow, and John M. Higgins, MD, associate pathologist, of the Center for Systems Biology and Department of Pathology at Massachusetts General Hospital, and colleagues have uncovered an association between mortality in patients with COVID-19 and elevated RDW at hospital admission and during hospitalization. Their report appears in JAMA Network Open.
Study Details
The researchers retrospectively analyzed RDW measurements in 1,641 adults who were admitted to Mass General or an affiliated hospital with COVID-19 between March 4 and April 28, 2020. Data collection ended on July 25, 2020.
Elevated RDW at Admission
- The mortality risk was 31% for patients whose RDW was >14.5% at admission and 11% for those with RDW ≤14.5% (RR, 2.73; 95% CI, 2.52–2.94)
- Patients with elevated RDW >14.5% at admission were 6.12 times more likely to die within 48 hours than those with normal RDW (4.9% vs. 0.8%)
Adjusted Mortality Risk
RDW >14.5% was associated with significantly increased risk of mortality even after adjustment for age, race, ethnicity, absolute lymphocyte count, D-dimer level and other blood count measures.
Another analysis incorporated five major comorbidities: chronic obstructive pulmonary disease, coronary artery disease, chronic kidney disease, diabetes and hypertension. The mortality risk associated with RDW >14.5% was greater than that for any comorbidity (HR, 2.01; 95% CI, 1.57–2.57; P < .001).
Increasing RDW During Hospitalization
- Admission RDW ≤14.5%—Patients with >0.5% increase in RDW during hospitalization had a 24% mortality rate compared with 6% for those with stable RDW
- Admission RDW >14.5%—Further increase in RDW during hospitalization was associated with a mortality rate of 40% and stable elevated RDW was associated with a mortality rate of 22%
- Nonsurvivors had an average RDW increase of 1.5% during their first week of hospitalization
RDW measurements at admission and during hospitalization may be helpful for determining which patients with COVID-19 need early, aggressive intervention. They may also be helpful for anticipating local hospital resource utilization.
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