Association between hospitalization for acute medical illness and VTE risk: A lower efficacy of thromboprophylaxis in elderly patients? Results from the EDITH case-control study

Introduction: Whether the association between hospitalization and venous thromboembolism (VTE) is modified by the use of thromboprophylaxis in older patients remains insufficiently evaluated. Our objective was to estimate VTE risk associated with hospitalization for acute medical illness depending on prescription of pharmacological thromboprophylaxis, in two different age categories using a 75years cutoff.

Methods: Using a case-control design, we estimated the risk for symptomatic VTE associated with hospitalization for acute medical illness depending on prescription of pharmacological thromboprophylaxis in two different age categories using a 75 years cut-off.

Results: 750 symptomatic VTE cases and their 750 age and sex-matched controls were analyzed. A total of 145 cases (19.3%) and 91 controls (12.1%) were hospitalized for acute medical illness in the preceding 3months prior to inclusion in the study (p<0.001). Hospitalization for acute medical illness was associated with a 75% increase in VTE risk: OR 1.75 (95% CI: 1.32-2.33). In patients <75years, there was a 2-fold increase in VTE risk associated with hospitalization when thromboprophylaxis was not prescribed: OR 2.01 (95% CI: 1.11-3.62), whereas no association was found when thromboprophylaxis was prescribed: OR 0.93 (95% CI: 0.44-1.95). In patients ≥75years, VTE risk associated with hospitalization remained significant whether or not thromboprophylaxis was prescribed: OR 2.69 (95% CI 1.28-5.66) and OR 2.02 (95% CI: 1.01-4.03) respectively.

Conclusion: Our results suggest that VTE prevention in acutely ill medical patients may be less effective in patients ≥75years. This finding needs to be addressed in further studies.