Deep venous thrombosis and ABO blood group are unrelated in trauma patients

ABO blood groups and thrombosis: a causal association, but is there value in screening?

ABO(H) antigens are expressed on red cells and on von Willebrand factor. An association between groups other than O and thrombosis exists: an effect that is predominantly mediated by von Willebrand factor. Overall, the risk of venous thrombosis associated with non-O has been estimated at 1.75-fold, with a higher risk (∼2.4-fold) in those with the least O(H) antigen (a combined group of A1A1/A1B/BB). Preliminary evidence also suggests that blood group may influence the venous thromboembolism risk associated with factor V Leiden. Overall, ABO(H) has a more modest effect on arterial disease, with a consistent effect observed in peripheral vascular disease and no influence evident with angina. A modest effect on myocardial infarction and stroke has been reported in some but not all studies. The potential mechanisms whereby blood group influences thrombosis, the limitations of current evidence and the current and future role of blood groups in identifying those at risk of arterial and venous disease is discussed.

ABO(H) blood groups and vascular disease: a systematic review and meta-analysis

BACKGROUND

Associations between vascular disease and ABO(H) blood groups have a long history, but no consensus exists regarding its magnitude and significance, or whether it relates to all disorders equally. An accurate calculation of risk would allow direct assessment of whether the effects of non-O status on thrombosis risk are of the magnitude predicted by its effect on von Willebrand factor/FVIII levels.

METHODS AND RESULTS

We conducted a systematic review and meta-analysis of studies reporting associations with non-O blood groups. This gave pooled odds ratios of 1.25 [95% confidence interval (CI) 1.14-1.36] for myocardial infarction (MI), 1.03 (95% CI 0.89-1.19) for angina, 1.45 (95% CI 1.35-1.56) for peripheral vascular disease, 1.14 (95% CI 1.01-1.27) for cerebral ischemia of arterial origin, and 1.79 (95% CI 1.56 to 2.05) for venous thromboembolism (VTE). However, restriction to prospective MI studies only did not confirm the association (OR 1.01; 95% CI 0.84-1.23), although these studies may have failed to capture early-onset disease. For VTE, using a combined group of OO/A(2)A(2)/A(2)O as index, the combination of A(1)A(1)/A(1)B/BB gave an OR of 2.44 (95% CI 1.79-3.33) and A(1)O/ BO/A(2)B an OR of 2.11 (95% CI 1.66-2.68).

CONCLUSIONS

This study confirms the historical impression of linkage between some vascular disorders and non-O blood group status. Although the odds ratios are similar to those predicted by the effect of ABO(H) on von Willebrand factor levels, further work is required to assess risk prospectively and to refine the effect of reducing O(H) antigen expression on thrombosis. However, as non-O and particularly A(1)A(1), A(1)B, BB constitute a significant proportion of the population attributable fraction of VTE, there may be a role for more widespread adoption of ABO(H) typing in testing strategies.