Findings from two Danish studies have shown that ABO blood type, both alone and in combination with the presence of factor V and prothrombin mutations, is associated with increases in risk for venous thromboembolism (VTE).
"ABO blood type had an additive effect on the risk of venous thromboembolism when combined with factor V Leiden R506Q and prothrombin G20210A mutations," say Børge Nordestgaard (Copenhagen University Hospital, Denmark) and colleagues.
Furthermore, ABO blood type was the most important risk factor for VTE in the general population, suggesting that blood type should be included in genetic screens for thrombophilia, they say.
The team analyzed the genotypes for ABO blood type, factor V Leiden R506Q and prothrombin G20210A among 66,001 participants who were followed up from 1977 to 2010, and found that the risk for VTE was 1.4 times greater among individuals with a non-O blood type than in those with an O blood type.
Among individuals with the factor V Leiden R506Q mutation, the risk for VTE was 2.2 and 7.0 times greater among heterozygous and homozygous individuals, respectively, compared with noncarriers. For those with the prothrombin G20210A mutation, the corresponding VTE risks were 1.5 and 11.0 times greater.
As reported in the Canadian Medical Association Journal, when the team combined ABO blood type with either the factor V Leiden R506Q or prothrombin G20210A genotype, there were stepwise increases in the risk for VTE. Similar increases were seen when combining the factor V Leiden R506Q and prothrombin G20210A genotypes.
Further analysis of the combined studies showed that the population-attributable risk for VTE was 20% for ABO blood type, 10% for factor V Leiden R506Q, and 1% for prothrombin G20210A.
The Factor V Leiden R506Q mutation causes factor V to be inactivated at a lower rate, leading to increased production of thrombin, while prothrombin G2021A is a mutation in the untranslated region of the gene promoter and leads to an increased production of prothrombin, explains the team.
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