Lipoprotein(a) as a Risk Factor for Venous Thromboembolism: A Systematic Review and Meta-analysis of the Literature

Elevated plasma levels of lipoprotein(a) (Lp(a)) are associated with increased cardiovascular risk in several clinical studies. However, there is a lack of data supporting a positive association between elevated Lp(a) levels and venous thromboembolism (VTE). Thus, we conducted a systematic review of the literature to better clarify its role as a risk factor for VTE. Medline and the Embase (up to May 2015) electronic databases were used to identify potentially eligible studies. Studies measuring Lp(a) values in adult patients with deep vein thrombosis and/or pulmonary embolism and in a population of patients without a VTE were selected. Studies on patients with major venous thromboembolic events occurring at other unusual site, case reports, and case series were excluded. The odds ratios (ORs) of the association between high values of Lp(a) and VTE and the weighted mean difference (WMD) in Lp(a) levels in cases and in controls were calculated using a random-effect model. Results were presented with 95% confidence interval (CI). Fourteen studies for a total of more than 14,000 patients were finally included in our analysis. Lp(a) was slightly but significantly associated with an increased risk of VTE (OR: 1.56, 95% CI: 1.36, 1.79; 10 studies, 13,541 patients). VTE patients had significantly higher Lp(a) values compared with controls (WMD: 14.46 mg/L, 95% CI: 12.14, 16.78; 4 studies, 470 patients). Lp(a) appeared to be significantly associated with increased risk of VTE. However, Lp(a) levels were only slightly increased in VTE patients compared with controls.