von Willebrand Factor-Ristocetin Cofactor Activity in Acute Myeloid Leukemia

Abstract

The AML is a hematopoietic stem cell disorder characterized by a block in differentiation of hematopoiesis, resulting in growth of a clonal population of neoplastic cells or blasts. Bleeding complications in AML patients is a common serious complication. It manifests in 40‐70% of AML patients at presentation. Factors associated with bleeding include thrombocytopenia, endothelial injury, excessive fibrinolysis, acquired hemophilia and adverse effect of drugs commonly used in the treatment. The vWF is a multimeric glycoprotein essential for normal hemostasis. It is synthesized in vascular endothelial cells, where it is stored in the Weibel‐Palade bodies and BM megakaryocytes, and is also present in platelets. It carries and protects coagulation factor VIII in the circulation, cross‐links platelets with exposed collagen at a site of vessel damage, and together with fibrinogen, it cross‐links platelets during subsequent platelet aggregation. The efficacy of vWF in primary hemostasis depends on its level and function. In this study, vWF‐RCo activity (functional vWF: a functional assay of plasma vWF based upon the degree of platelet agglutination induced 66 after the addition of ristocetin) was assessed in newly‐diagnosed (de novo) AML patients and after two weeks post‐chemotherapy, and this activity was correlated with haemostatic complication, known prognostic factors and outcome in AML patients. The study was carried out during 2013‐2014. It was a crosssectional case control study carried on 30 AML patients and 10 age‐ and sex‐matched healthy subjects (as a control group). The AML patients were subjected to full history taking laying stress on bleeding manifestations, clinical examination and laboratory investigations [such as CBC, PT, APTT, FDPs, cytochemical staining, and immunophenotyping (Lichtman and Liesveld, 2010a). The vWF‐RCO activity was measured, in both groups, using platelet agglutination method (Siemens Health care Diagnostics Products, Marburg/ Germany). All data were collected, tabulated and statistically analyzed. Results showed that the vWF‐RCO activity among AML patients ranged from 52.8 to 100.6%, with a mean value of 80.5 ±12.6. Meanwhile, the range in the control group was from 90.8 to 126.4% with a mean value of 99.5 ±10.5%. A statistically highly significantly (p<0.001) lower mean vWF‐RCO activity was documented among the patients' group when compared to the controls, and a statistically significantly increased activity that almost returned to normal after two weeks of treatment. Moreover, a statistically significantly reduced vWF‐RCO activity was found in AML patients with bleeding symptoms versus non‐bleeders. Also, there was a statistically significantly reduced vWF‐RCO activity in AML patients with bad outcome.