CMAAO Coronavirus Facts and Myth Buster: RDW Biomarker Cut Off 14.5%
Dr KK Aggarwal, 27 September 2020
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With input from Dr Monica Vasudev
(DG Alerts Excerpts)
1093: Red blood cell distribution width: Potential COVID-19 biomarker for mortality risk
- Red blood cell distribution width (RDW) may help in stratifying mortality risk among patients infected with severe COVID-19, suggests a study published in JAMA Network Open.
- Researchers noted that in a cohort of hospitalized COVID-19 patients, those with RDW > 14.5% at admission had a 31% mortality risk, while those with an RDW of <14.5% had a mortality risk of 11%. The relative risk (RR) of mortality in the entire cohort was 2.73 (95% CI, 2.52-2.94, p<0.001).
- The association was independent of D-dimer levels, absolute lymphocyte count, demographic factors, and common comorbidities.
- Elevated RDW seems to be a nonspecific marker of illness with the potential to yield general quantitative risk stratification.
- The study enroled 1641 adults with SARS-CoV-2 infection admitted to 1 of 4 hospitals in the Boston, Massachusetts area (Massachusetts General Hospital, Brigham and Womens Hospital, North Shore Medical Center, and Newton-Wellesley Hospital) from March 4 to April 28, 2020; mean age 62 years. About 54% of the participants were men, 45% were White individuals and 30% Hispanic; 17% of patients in the cohort died.
- The main outcome was patient survival during hospitalization. Measures included RDW at admission and during hospitalization, with elevated RDW defined as >14.5%.
- Patients with elevated RDW at admission had 6.12 times higher likelihood of dying within 48 hours (23 of 470 patients [4.9%]) compared to patients with a normal RDW (9 of 1175 patients [0.8%]).
- Previous studies have reported that raised D-dimer levels and low absolute lymphocyte counts are associated with an increased mortality risk. In the present study, risk of mortality associated with RDW remained statistically significant after adjusting for patient age, race, ethnicity, D-dimer level, absolute lymphocyte count, other blood count measures, and 5 major comorbidities.
- A rising RDW during hospitalization was tied to a heightened risk of death than if RDW did not change. The mortality risk rose from 6% to 24% for those with a normal RDW at admission, and from 22% to 40% for those having elevated RDW at the time of admission. Few patients experienced > 2% increase per week in RDW during hospitalization. The large increase in the elevated RDW group raises the odds of a longer disease duration among these patients at the time of admission.
- RDW elevation occurs as a result of delayed clearance of older red blood cells. COVID-19 is associated with altered turnover in all WBC (white blood cell) lineages, as well as with alteration in platelet dynamics in COVID-associated coagulopathy. The association of elevated RDW with COVID-19 severity could be consistent with previous reports (in non–COVID-19 cohorts), indicating that RDW can rise when RBC production kinetics have slowed in the setting of increased WBC and platelet kinetics.
- Patients with several different underlying acute and chronic illnesses can have a higher baseline RDW, and it is possible that the RDW measured at admission is a nonspecific summary marker of the presence of these illnesses. Irrespective of the reasons for the differences in RDW at admission, the association of elevated RDW with increased mortality risk seems to persist after admission.
Reference: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2770945
SOURCE: JAMA Network Open
Dr KK Aggarwal
President CMAAO, HCFI and Past National President IMA
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Serial CBC s can be done in rural set up & with other inexpensive markers patients can be followed .