One of the big challenges healthcare workers are facing in this global pandemic is identifying those COVID-19 patients most at risk of severe illness and death. COVID-19 certainly is more dangerous, on average, in the elderly or those with pre-existing health problems, but that doesn’t preclude a 96-year-old from presenting with no symptoms, or a healthy 21-year-old losing her life. A team of researchers from Massachusetts General Hospital have been trawling through hospital admission data to find some way to help doctors better assess those patients most at risk of suffering the worst effects of the disease.
The researchers analyzed blood samples from 1,641 patients admitted to Boston hospitals with COVID-19 earlier this year. The plan was to closely study the samples to identify any particular molecular patterns that could predict disease severity. Before looking at more complicated blood-based biomarkers the researchers first looked at biomarkers gathered in the most routine blood tests.
"We were surprised to find that one standard test that quantifies the variation in size of red blood cells – called red cell distribution width, or RDW – was highly correlated with patient mortality, and the correlation persisted when controlling for other identified risk factors like patient age, some other lab tests, and some pre-existing illnesses," says co-author on the new study, Jonathan Carlson.
RDW is a very common metric gathered in most standard blood count tests. The new study found patients displaying an elevated RDW at time of admission were 2.7 times more likely to die from COVID-19. Elevated RDW was also more significantly associated with mortality in younger COVID-19 patients.
The study also notes that patients whose RDW was seen to increase during hospitalization were more likely to suffer worse outcomes from the disease. The researchers suggest this indicates RDW may be a useful biomarker to track the progress of a patient while admitted in hospital.
RDW has been previously determined to be an effective non-specific biomarker of illness, and the researchers do note it is unlikely there is a direct causal relationship at play. But, what is important here is the routine nature of RDW measurements gathered in common blood testing.
A number of similar studies have been published over the past few months exploring blood-based biomarkers to identify patients most as risk of death or severe illness from COVID-19. Many researchers have homed in on particular blood biomarker patterns that can be associated with the worst outcomes, however, not many of those blood measurements are as simple and routine to collect as RDW measurements.
The finding needs further validation in broader cohorts of patients, but if confirmed, this simple laboratory test may be a useful way to detect those COVID-19 patients most in need of clinical care.
The new research was published in the journal JAMA Network Open.
Source: Massachusetts General Hospital