Association between inherited thrombophilia and venous thromboembolism in patients with non-O blood type: a meta-analysis.

INTRODUCTION: Hereditary conditions, including non­O 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 meta­analysis was carried out to find out if simultaneous occurrence of FVL or PTM and the non­O 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/non­O group and PTM/non­O group, respectively. Pooled odds ratios (OR) and 95% CIs were obtained by a random­effects model. RESULTS: Nearly 6% of the enrolled patients manifested both FVL and the non­O group, whereas only 1.4% had PTM and the non­O group. The VTE risk was considerably amplified in FVL and the non­O 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 non­O 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 co­occurrence of FVL and the non­O group enhances the risk of VTE that could have clinical influence and drive therapeutic corrections. The coexistence of PTM and the non­O blood group seems to play a less important role in the incidence of VTE.