Introduction: Hereditary conditions, including non‑O blood group or thrombophilic alterations such as factor V Leiden (FVL) and G20210A prothrombin mutation (G20210A PTM), are usually considered risk factors for venous thromboembolism (VTE).
Objective: This meta‑analysis was carried out to find out if simultaneous occurrence of FVL or PTM and the non‑O blood group may increase the risk of developing VTE.
Patients and methods: MEDLINE and EMBASE databases were explored until March 2021. Eleven publications, comprising 82 465 patients, and 6 studies, including 70 004 patients, were analyzed to evaluate the association between FVL/non‑O group and PTM/non‑O group, respectively. Pooled odds ratios (OR) and 95% CIs were obtained by a random‑effects model.
Results: Nearly 6% of the enrolled patients manifested both FVL and the non‑O group, whereas only 1.4% had PTM and the non‑O group. The VTE risk was considerably amplified in FVL and the non‑O group (OR, 5.94; 95% CI, 5.33-6.61; P <0.01), more than if just 1 of these 2 risk factors was present. The equivalent population attributable risk (PAR) of VTE was around 21%. The patients with PTM and the non‑O group manifested a significantly augmented risk of VTE (OR, 4.01; 95% CI, 3.00-5.36; P = 0.01), although PAR was considerably lower (3.7%).
Conclusions: The co‑occurrence of FVL and the non‑O group enhances the risk of VTE that could have clinical influence and drive therapeutic corrections. The coexistence of PTM and the non‑O blood group seems to play a less important role in the incidence of VTE.