The Correlation of Lewis Antigens With VTE

The goal of this observational study is to learn if certain factors in a person's blood are linked to a history of venous thromboembolic disease (VTED), which includes conditions like deep vein thrombosis. Lewis system antigens are natural markers found on red blood cells. Past research suggests that people without these specific markers might have a higher chance of developing heart disease, but the link to blood clots in veins is not well understood. This study aims to answer: * Are certain Lewis antigen types more common in people with a history of VTE? * Do the Lewis antigen results relate to other known blood clot risk factors? Researchers will identify Lewis a and b antigens in 100 participants who attend the Haemostasis Disorders Clinic at the University Hospital of Larissa. All participants are people with a personal history of deep vein thrombosis, with or without an inherited or acquired tendency for blood clots. Researchers will also record other known risk factors for VTED for each participant. This study is self-funded.