Identify the procoagulant profile in immune thrombocytopenic patients with thrombosis.

Clinical implications of antiphospholipid antibodies in ITP patients with thrombosis.

Diagnostic role of microparticles in ITP patients with thrombosis.

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by isolated thrombocytopenia and an increased risk of bleeding. Paradoxically, ITP is also associated with an increased risk of thrombosis (1).

Recent studies showed that the occurrence of thrombosis in patients with ITP is not purely accidental and can be considered a clinical reality with an important impact on the management of the disease (2).

The pathophysiological mechanism for thrombosis in ITP remains unclear. Sever bleeding episodes are relatively rare in some patients with ITP although having low platelet count, suggests that these patients may have a protective factor against bleeding (3).

Antiphospholipid (aPL) antibodies are a heterogeneous group of autoantibodies with high affinity for phospholipids such lupus anticoagulant (LA), β2glycoprotien І (β2GPІ), and anticardiolipin (anti-CL). They interfere with physiological mechanisms of coagulation and fibrinolysis, leading the haemostatic balance towards coagulation. Moreover, it seems to affect the physiological function of various cells such as platelets and endothelial cells (4).

Microparticles (MPs) are a diverse group of bioactive small-sized vesicles (100-1000nm) that can be found in body fluids and blood after activation, necrosis, or apoptosis of almost all cells. Although most MPs in human blood originate from platelets, MPs are also released from leukocytes, erythrocytes, endothelial cells, smooth muscle cells and cancer cells (5). They participate in intercellular communication and play a major role in homeostasis under physiological conditions and also in diseases (6). The most prominent property of MPs is their procoagulant potential, mainly based on phosphatidylserine exposure and tissue factor expression (7).

Elevated levels of antiphospholipid antibodies and microparticles have been reported as a risk for development of prothrombotic state (8).

Patients with confirmed diagnosis of primary chronic ITP with and without thrombosis, male or female above age of 18.Inclusion Criteria:

Exclusion Criteria:

Thrombocytopenic patients due to secondary causes such as pregnant women, patients with uncontrolled hypertension, peripheral or coronary artery disease, abnormal hepatic or renal function tests, bleeding disorder, and thrombopathy well be excluded from the study.

Patients full fill the criteria of antiphospholipid syndrome (APS).

The study will include 35 cases of ITP without thrombosis and 35 case of ITP with thrombosis.

The sample size was calculated based on determining the main outcome variable using G*power software 3.1.9.2. based on the following assumption:

Main outcome variable is difference between procoagulant profile of ITP patients with and without thrombosis especially for levels of antiphospholipid antibodies and microparticles (9).

Main statistical test is one-sided student t-test to detect the difference between groups.