Baseline Thrombocytopenia Associated With Mortality Risk in VTE

Moderate-to-severe thrombocytopenia at baseline is associated with significant risk for major bleeding and all-cause death in patients with venous thromboembolism (VTE), according to a study published in The American Journal of Cardiology. Baseline thrombocytopenia was not associated with risk for recurrent VTE events in this population.

Authors of this large cohort study sought to determine the association of baseline thrombocytopenia with long-term clinical outcomes, including the risk of bleeding, recurrent VTE, and mortality, in patients diagnosed with VTE.

The study cohort included 3012 patients with available baseline platelet counts who were enrolled in Japan’s COMMAND Venous Thromboembolism Registry. Baseline thrombocytopenia was defined by a platelet count of 150,000/µl or less and was further classified as mild (100,000/µl to 150,00/µl), moderate (50,000/µl to 99,9999/µl), or severe (<50,000/µl).

Participants were followed for a median 1219 days. The study investigators compared clinical characteristics, management strategies, and long-term outcomes among the 3 thrombocytopenia groups. Major bleeding, as defined by the International Society of Thrombosis and Hemostasis, was the primary study outcome measure; recurrent VTE and all-cause death were secondary outcome measures.

To adjust for variables, researchers used the multivariable Cox proportional hazard model to calculate the hazard ratio (HR) for risk associated with thrombocytopenia.

Of the 3012 participants, 167 (5.5%) patients were diagnosed with moderate to severe thrombocytopenia (144 moderate and 23 severe), 523 (17.4%) with mild thrombocytopenia, and 2322 (77.1%) with no thrombocytopenia.

Over a 5-year period, patients with moderate to severe thrombocytopenia had a higher incidence of major bleeding than patients with mild or no thrombocytopenia (29.4% vs 14.1% vs 10.6%; P <.001). Adjusting for variables, moderate to severe thrombocytopenia relative to no thrombocytopenia was significantly associated with risk of major bleeding (HR, 2.15; 95% CI, 1.43-3.13; P <.001) as well as for mortality (HR, 1.54; 95% CI, 1.18-1.97; P =.002).

Across all 3 groups, the associated risk for recurrent venous thromboembolism was insignificant (HR, 1.05; 95% CI, 0.55-1.81; P =.87), even after adjusting for confounders.

Limitations of the study included arbitrary platelet count cut-off values for classifying thrombocytopenia — although they were based on relevant literature and clinical findings — and not evaluating the change in platelet count over time, especially during major bleeding events.

Platelet function was not evaluated, nor was the cause of thrombocytopenia, possibly influencing clinical outcomes. Patients with moderate to severe thrombocytopenia made up a small proportion of the study population.

Study authors concluded that that patients with VTE who were classified with moderate to severe thrombocytopenia at baseline were associated with increased risk for major bleeding events and all-cause mortality, but were without significant increased risk for recurrent VTE.

The COMMAND VTE Registry used in this study was sponsored by the Research Institute for Production Development, Kyoto, Japan, and by Mitsubishi Tanabe Pharma Corporation, Osaka, Japan.

Reference                                                                                                                       

Yamashita Y, Morimoto T, Amano H, et al. Influence of baseline platelet count on outcomes in patients with venous thromboembolism [published online September 14, 2018]. Am J Cardiol. doi:10.1016/j.amjcard.2018.08.053