Studies contradict earlier findings on blood group and COVID-19 severity, mortality
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Understanding risk factors for COVID-19 susceptibility and severity has been an ongoing objective of researchers during the pandemic.
ABO blood group has been one focus of research, with studies showing that individuals with blood type A may be more likely to develop COVID-19 and have poor outcomes.
However, two studies presented at the virtual ASH Annual Meeting and Exposition showed no significant association between blood group and COVID-19 severity.
“We found that ABO blood group and Rhesus factor were not associated with disease mortality, disease severity or use of mechanical ventilation,” Aula Ramo, MD, a resident in the department of internal medicine at Henry Ford Hospital, said in an interview with Healio. “We also looked at predictors of mortality in part of our study, and found that age over 65 years, Caucasian race and male gender were statistically significant predictors of mortality.”
In another study presented at ASH, researchers at Rush University Medical Center sought to determine whether patients with COVID-19 and certain blood groups had a greater risk for thrombosis or higher rates of mortality.
“There were some initial studies that said certain blood types are a predictor for higher susceptibility for COVID-19,” Rush researcher Shivani Rao told Healio. “After that, the next logical question to ask is what may predispose the patient to greater severity of disease. One of the things we’ve seen a lot clinically is that thrombosis is commonly a marker of severity. So, we wanted to look into whether blood type may predispose a patient to thrombosis.”
More prominent factors
The Henry Ford Hospital study showed that demographic and clinical factors other than blood group appeared associated with COVID-19 severity.
For the study, Ramo and colleagues evaluated records of hospitalized patients with COVID-19 treated at the institution between March 10 and April 30. The analysis included 1,488 eligible patients (median age, 68 years; range, 19-99; 54% women, 58% Black) with diverse backgrounds. Researchers used univariate and multivariate logistic regression to analyze variables such as age, sex, race, ABO blood group, comorbid conditions, disease severity (based on ICU admission) and intubation as predictors of mortality, based on survival data updated July 15.
About one-third of patients (32.6%; n = 485) had blood type A, whereas 276 (18.5%) had blood type B, 658 (44.2%) had blood type O, and 69 (4.6%) had blood type AB.
Among the 469 patients (31.5%) who required ICU admission, 370 were intubated. By last follow-up, 411 patients (27.6%) had died.
Results showed no association between ABO blood groups and Rhesus factor and ICU admission, intubation or death. However, multivariate analysis revealed significant associations of mortality with age of 65 years or older (OR = 4.27; 95% CI, 3.19-5.71), male sex (OR = 1.57; 95% CI, 1.23-2.01), white race (OR = 1.46; 95% CI, 1.14-1.86) and chronic obstructive pulmonary disease (OR = 1.49; 95% CI, 1.09-2.04).
Researchers noted that Black patients appeared nearly 40% less likely to die than white patients (OR = 0.56; 95% CI, 0.44-0.7).
Ramo said although COVID-19 severity may be affected by socioeconomic circumstances, these factors are difficult to quantify. She said the definition of “disease severity” has evolved over time.
“Admission to the ICU, which has been used as an indicator of disease severity, has really changed since the beginning of the pandemic,” she said. “It continues to vary based on availability and workflow at hospitals.”
Thrombosis and COVID-19
For the retrospective study conducted at Rush University Medical Center, researchers reviewed the records of 1,265 patients with COVID-19 who underwent treatment at the institution between March 1 and June 26.
The analysis included 138 patients who had a thromboembolism confirmed by imaging. A total of 102 patients with thrombosis and 402 without thrombosis had known blood types that were used in the analysis.
The researchers found no significant variation in blood type prevalence among patients with COVID-19 vs. the general population without COVID-19 (type A, 34.3% vs. 32.7%; type AB, 2.9% vs. 4.2%; type B, 16.7% vs. 14.9%; type O, 46.1% vs. 48.1%). Similarly, results showed no significant difference among blood types in incidence of thrombosis (type A, 23.3%; type AB, 15%: type B, 20.7%; type O, 18.7%) or mortality (type A, 20.7%; type AB, 15%; type B, 13.4%; type O, 21.8%).
Regarding her study’s different findings on blood type compared with previous reports, Rao said her study was limited by its small sample size.
“We started with more than 1,000 patients who were COVID-19 positive between March and June at our institution. We ended up with only about a hundred patients who had reported blood types and experienced thrombosis,” she said. “That’s a very small percentage of what we originally started with. I think in future studies, we would want to study a bigger population of patients with thrombosis.”
Study co-author, Shivi Jain, MD, assistant professor of internal medicine in the division of hematology and director of diagnostic bone marrow services at Rush University Medical Center, also noted that patients with COVID-19 and thrombosis generally are sicker.
“To get blood typing, you would have to have some threshold of severe disease,” she said. “So, that may have skewed how we collected data, since only a small number of the original 1,000 or so patients had reported blood types.”
Rao said the study reflects an overall effort to learn more about the factors involved in COVID-19 severity.
“That’s precisely why we wanted to conduct this study. The risk factors for COVID-19 are somewhat known, but we feel it is very important to also look into more factors, such as blood type, that affect COVID-19 severity,” she said.
References:
Ramo, et al. Abstract 104. Presented at: ASH Annual Meeting and Exposition (virtual meeting); Dec. 5-8, 2020.
Rao, et al. Abstract 244. Presented at: ASH Annual Meeting and Exposition (virtual meeting); Dec. 5-8, 2020.
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Ramo, et al. Abstract 104. Presented at: ASH Annual Meeting and Exposition (virtual meeting); Dec. 5-8, 2020.
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