Risk of recurrent VTE
Twenty-three studies (n = 8,080) compared risk of recurrent VTE in people with and without mutations. Study quality was classed as moderate. Risk of recurrent VTE was significantly increased in probands who were heterozygous (pooled OR 1.56, 95% CI: 1.14, 2.12, with significant heterogeneity) and homozygous (pooled OR 2.65, 95% CI: 1.18, 5.97) for factor V Leiden. No significant difference was found for probands who were heterozygous for thrombin G20210A (pooled OR 1.45, 95% CI: 0.96, 2.21).
Risk of VTE in family members
Seventeen studies (n = 7,667) compared risk of VTE in family members with and without mutations. Study quality was mixed. Family members who were heterozygous (pooled OR 3.49, 95% CI: 2.46, 4.96; six studies) and homozygous (pooled OR 17.84, 95% CI: 7.98, 39.89; five studies) for factor V Leiden had significantly greater odds of first VTE than those without the mutation.
Impact of testing on outcomes
No studies directly assessed the impact of testing on VTE-related outcomes. Evidence from four studies indicated that anticoagulation decreased VTE recurrence among probands with either mutation. Four qualitative or survey studies found that testing had little impact on knowledge or behaviour and testing was not associated with significant distress, although one study found an increase in worry after testing in people with a previous VTE.
No evidence of publication bias was found. Results of other analyses were reported.