1. Venous Thromboembolism Unit, Internal Medicine Department, General University Hospital Gregorio Marañón, 28007 Madrid, Spain
2. School of Medicine, University Complutense of Madrid, 28007 Madrid, Spain
3. Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain
4. Department of Clinical Biochemistry, General University Hospital Gregorio Marañón, 28007 Madrid, Spain