Race, ABO Blood Type, Gender, Age and Venous Thromboembolism Risk: Not Black and White

Venous thromboembolism (VTE) prevalence has been noted to be different for different racial groups: Non-Hispanic blacks tend to have a higher risk compared with non-Hispanic whites. Different ABO blood types have also been previously shown to be associated with different risk of VTE, with individuals with O blood type carry the lowest VTE risk. Given that blacks have a higher percentage of O blood type, one would expect to see a lower prevalence of VTE. In order to explain this paradoxical finding, we utilized the Clinical Looking Glass (CLG) system to study the relative influence of race, gender, age, and ABO blood type on the VTE risk. A total of 61,077 adult patients admitted to our large diverse urban hospital between 2000 and 2009 who had blood typing performed were included in the study. Four cohorts were established according to ABO blood group and the prevalence of VTE among each cohort was examined. We confirmed the higher prevalence of VTE in blacks (7.05% vs. 6.75%, p<0.001). While it has been previously shown that male gender is associated with higher VTE risk, we found this to be true only for the younger patient population: in adult patients less than 45yrs, male carried a higher prevalence of VTE (5.97% vs. 3.06%, p<0.001); in patients aged between 45 and 64yrs, no gender difference in the prevalence of VTE could be determined (8.40% vs. 8.33%, p=0.86). For patients aged between 65 and 84yrs, male gender was actually associated with lower prevalence of VTE (10.11% vs. 12.07%, p=0.009). No gender difference was seen in patients older than 80 (11.11% vs. 11.99%, p=0.356). When the prevalence of VTE was examined within each blood type, we confirmed that O blood type in general carries a lower VTE risk compared with other non-O blood types (6.9% vs. 8.4%, p<0.001); this held true for both genders (See Figure). To better analyze this complex interaction between race, ABO blood type, gender, age and VTE risk, we used logistic regression analysis. Race appeared to be the strongest determinant (black vs. white OR 1.43; 95% CI: 1.33, 1.52), followed by ABO blood type (Type A 1.2, 95% CI: 1.13–1.3; Type AB 1.2, 95% CI: 1.05, 1.40; Type B 1.33, 95% CI 1.23, 1.44), then gender (male vs. female OR 1.11; 95% CI: 1.04, 1.18) and finally, age (OR 1.03; 95% CI 1.03 – 1.03).). In conclusion, VTE risk for any individual is a composite of multiple variables. Our study suggests that race, gender, ABO blood type and age might allow us, in combination with other known risk factors, to develop a prognostic score for VTE risk stratification for each patient.