The Influence of Body Weight on Clinical Outcome of Patients with Venous Thromboembolism: Findings from a Prospective Registry (RIETE).

Introduction Patients who are underweight or obese are often excluded from clinical trials of venous thromboembolism (VTE) treatment. Thus, recommendations based on evidence from these trials may not be optimal for patients at these two extremes of body weight. The Registro Informatizado de la Enfermedad TromboEmbólica (RIETE), initiated in March 2001, is a multicenter, observational registry gathering data on treatment practices and clinical outcomes in patients with objectively confirmed, symptomatic, acute VTE. The aim of this analysis was to examine the influence of body weight on clinical outcomes of patients with VTE.

Methods Patients with objectively confirmed, symptomatic, acute VTE are consecutively enrolled into the RIETE registry. Patients are excluded if they are participating in a therapeutic clinical trial or are not available for 3-month follow-up. For this analysis, data from patients in the following ranges of body weight were examined: <50 kg, 50–100 kg, and >100 kg.

Results As of December 2003, 6128 patients with acute VTE were enrolled from 94 participating centers. Of these, 122 (2%) weighed <50 kg, 5827 (95%) weighed 50–100 kg and 179 (2.9%) weighed >100 kg. Patient characteristics are presented in table 1. Incidences of recurrent VTE, bleeding complications (fatal, major, or minor), or fatal PE were similar between groups. However, the incidence of the composite endpoint of VTE recurrence and/or major bleeding was higher in patients <50 kg than 50–100 kg (7.4% vs 3.3%, respectively; p=0.01). Overall mortality during the first 15 days of treatment was higher in patients <50 kg than 50–100 kg (9.8% vs 2.7%, respectively; p<0.001). There were no significant differences in clinical outcomes between the >100 kg and 50–100 kg groups.

Conclusion Although there were no differences in the incidences of recurrent VTE, bleeding complications or fatal PE between groups, patients with VTE, weighing <50 kg had a higher overall mortality and a greater incidence of the composite endpoint of VTE recurrence and/or major bleeding compared with patients weighing 50–100 kg. The higher incidence of cancer, immobility, and/or the use of corticosteroids or NSAIDs, may explain the poor outcome in this patient group.

Table 1. Patient characteristics