In patients with a chronic renal disease at the terminal stage, extrarenal epuration is essential for the control of clinico-biological complications. Two extrarenal epuration techniques are currently available: peritoneal dialysis (using the peritoneal membrane of the patient) and hemodialysis, requiring the use of an external biocompatible membrane known as 'dialysis filter'. This technique requires a vascular access (arteriovenous fistula or dialysis catheter). The thrombosis of vascular accesses represents a major cause of morbidity and mortality in hemodialysis patients. Thrombosis are more frequent when using synthetic prosthetic arteriovenous fistula instead of native arteriovenous fistula.

Antiphospholipid Syndrome (APLS) is a rare autoimmune disease characterized by arterial thrombosis, venous thrombosis and obstetrical complications such as as defined by the Sidney's criteria.

In the general population, the presence of antiphospholipid antibodies is associated with an increased risk of thromboembolic events. In the nephrological population, this prevalence is higher in hemodialysis patients compared to patients on peritoneal dialysis or non-dialyzed patients. Up to 37% of hemodialysis patients are positive for antiphospholipid antibodies and this biology is associated with thrombotic events and vascular access thromboses. However, some studies do not report this association and there is currently no consensus in terms of the therapeutic management of these patients.

Some factors influencing the positivity for antiphospholipid antibodies have been reported: smoking, age, the presence of a non-glomerular nephropathy, hypoalbuminaemia, the use of a central venous catheter for dialysis or the use of a non-biocompatible dialysis membrane.

Taking into account the conflicting data from the literature, it seems important to study the respective role(s) of 3 types of antiphospholipid antibodies in the occurrence of thrombo- embolic events in patients undergoing dialysis within the CHU Brugmann Hospital.

Inclusion Criteria:

- All patients undergoing dialysis within the CHU Brugmann Hospital

Exclusion Criteria:

• Mutation of factor V
• Mutation G20210A of the prothrombin gene
• Protein C deficiency
• Protein S deficiency
• Antithrombin III deficiency

All patients undergoing dialysis within the CHU Brugmann Hospital.