On 2020-09-30 15:25:51, user Sinai Immunol Review Project wrote:
Very interesting paper!
Main Findings<br />
In this preprint, Zietz and Tatonetti explore the relationship between blood type and risk of SARS-CoV-2 infection, disease severity, and mortality. Using data from the electronic health records (EHR) of 1,559 patients who presented with suspected COVID-19 (with only 682 who tested SARS-CoV-2 positive) at New York Presbyterian Hospital (NYP), they analyzed four outcome pairs. Two pairs were used to test risk for infection: i) positive for infection vs negative for infection and ii) positive for infection vs general patient population. Another pair was used to test for infection severity: iii) positive patients intubated (179) vs positive patients not intubated. The last pair was used to test risk of infection-related death: iv) deceased vs surviving patients. As a measure of exposure, they used ABO blood type (A, B, AB, or O) alone or with Rh factor. In total, they generated eight contingency tables, two for each outcome pair, one with Rh and one without. Blood type was found to be significantly associated with SARS-CoV-2 infectivity after chi-squared analysis of positively vs negatively tested patients (p=0.006 for ABO system and p=0.031 for ABO+Rh system). To identify specific blood types that may predict viral test outcomes, they specifically tested each blood type against those of a different blood type for all four outcome pairs tested in the chi-squared analysis. Fisher-exact test showed that a significantly higher proportion of patients with the blood type A tested positive for the virus, and a lower proportion of patients with O and AB tested positive (p=0.009, 0.036, 0,033 respectively). When the Rh factor was included in the analysis, Rh-positive patients with the blood type A were at a 38.2% higher risk for testing positive (p=0.004), while those with the blood type O were at a 21.0% lower risk (p=0.024). Furthermore, they performed a meta-analysis by pooling data from NYP and Zhao et al’s data from China, which substantiated the findings on blood types A and O in a random-effects analysis that compared the positively infected patients with the general populations of NYP (USA), Wuhan, and Shenzhen (China) (OR=1.164, p=0.0291, for A, and OR=0.7252, p=0.0012 for O). This analysis also revealed a new increased risk of testing positive for those with blood type B (OR=1.1101, p=0.0361). Logistic regression models confirmed that although other risk factors such as diabetes, age, and obesity correlate with certain blood types, adding the blood type as a variable to the model significantly strengthens the prediction for SARS-CoV-2 positive versus negative outcome. On the other hand, blood type was not found to be a risk factor for disease severity or mortality in any of the analyses.
Limitations<br />
The study should be considered in the context of its limitations. Firstly, blood type-disease association was significant when comparing patients who tested positively for COVID-19 to those who tested negative, but the result was not replicated when comparing positively-tested patients to the general patient population. As the authors note, only a specific population received testing for COVID-19 while the majority of the patients in the EHR system were never tested, which could explain the discrepancy. Another related limitation is that the sample meant to be representative of the general population consisted only of people in NYP’s EHR database, which may be biased toward a specific population, and it is therefore unclear if the results would replicate in another cohort. Additionally, the finding that AB blood type is associated with lower risk of infection can only be taken as preliminary; the sample size was quite small (only 4.4% of the cohort had that blood type), and the result was not replicated in the meta-analysis with the data from China. Furthermore, the analyses that included Rh factor, the sample sizes for all Rh-negative subtypes were also small, and there were no patients with AB-negative blood who tested positive for the virus. This highlights the necessity for larger cohorts from multiple sites, but the preliminary results are promising.
Significance<br />
This preprint on NYP patients supports the previous results by Zhao et al on Chinese Wuhan and Shenzen patients that showed that individuals with the blood type A are at a greater risk of testing positive while those with type O are at a lower risk. As the authors reported, blood type distribution is different in NYP than in China, this substantiates their results and indicates it may be replicable in other geographical and ethnic populations despite blood type heterogeneity. Furthermore, they provide a more detailed picture through a meta-analysis with both NYP and China data, and include the Rh factor in the NYP analysis. Notably, they introduce new findings: a decreased risk for testing positive for those with AB blood in the NYP-only analysis, and an increased risk in those with blood type B in the pooled analysis. With the use of convalescent serum as a disease therapeutic, the knowledge that those with A-positive and B blood types may be at an increased risk of contracting COVID-19 can help ensure that sufficient amounts of plasma donors are compatible with that blood type. Finally, the study shows that blood type is not a significant predictor of disease prognosis in those infected with SARS-CoV-2, highlighting the need for other immunological and serological predictors of disease severity and mortality.
Credit<br />
Reviewed by Miriam Saffern as part of a project by students, postdocs and faculty at the Immunology Institute of the Icahn School of Medicine, Mount Sinai.