von Willebrand factor ristocetin cofactor (VWF:RCo) assay: implementation on an automated coagulometer (ACL).

BACKGROUND: VWF:RCo assay is the standard and widely used laboratory test for von Willebrand disease (VWD) diagnosis. It is hampered by high intra- and inter-assay imprecision and is time consuming. Automation may improve the assay performance and allow its routine application. OBJECTIVE: Automation of VWF:RCo on the ACL 7000 coagulometer (Instrumentation Laboratory, Milan, Italy) and its evaluation in VWD diagnosis. METHODS AND MATERIALS: Method performance determination: precision, detection limit (DL), interferences, dose-response curve. Method comparison: analysis of 105 plasma samples from normal subjects (50), VWD type 1 (24), VWD type 2 (24) and VWD type 3 (7) with ACL VWF:RCo and comparison with the reference aggregometric (AGM) method. RESULTS: ACL VWF:RCo: CVs around 10% vs. 19% of AGM method; DL: 0.08 U mL(-1); potential interferences from bilirubin, triglycerides and hemoglobin, avoided by suitable plasma dilution; high correlation with AGM VWF:RCo (Deming regression Y =-0.0277 + 1.0519X) either in normal or VWD plasmas. In VWD types 1 and 2, the VWF:RCo/VWF:Ag ratios are >0.6 or <0.6, respectively, when calculated with both AGM and ACL VWF:RCo values. CONCLUSIONS: The automated VWF:RCo on the ACL 7000 coagulometer shows precision improvement and high correlation with the reference AGM method. The test allows the diagnosis of both quantitative (VWD types 1 and 3) and qualitative (VWD type 2) forms of the disease. These results and the assay feasibility make it a suitable and reliable test for the routine diagnosis of VWD.

Abnormal platelet von Willebrand factor (vWF) as a marker of abnormal function in megakaryocytic dysplasia.

The myelodysplastic syndromes (MDS) are neoplastic disorders of the hemopoietic system; multilineage involvement is also evidenced by specific cellular dysfunctions. The von Willebrand factor (vWF), synthesized and processed in the megakaryocytes (MK), is stored in the alpha granules of the platelets. The platelet vWF multimeric pattern was studied in 18 patients with MDS, and in 4 with pernicious anemia (PA), to investigate whether the processing of vWF is abnormal in the megakaryocytic dysplasia. An abnormal multimeric pattern was observed in 10/18 MDS and 4/4 PA patients. The abnormality of this specific protein is the discrete expression of the basic disorder, and is reversible when hemopoiesis is normalized. Although the data do not allow any conclusion, abnormal synthesis is the likely explantation of the abnormality.