title: Evaluation of two automated methods for measurement of the ristocetin cofactor activity of von Willebrand factor.
abstract: We have evaluated two automated methods for measuring ristocetin cofactor activity (VWF:RCo) on an automated coagulation analyzer (STAR, Diagnostica Stago Inc., Parsippany, NJ). A modification of the BC von Willebrand Reagent method (Dade Behring Inc., Newark, Delaware) was compared with a standard method using a platelet aggregometer, and an in-house automated method was developed using commercially available components. The STAR measures the change in optical density (OD) caused by agglutination of platelets. Change in OD was linear for plasma dilutions between .25 and .04 U/mL. Coefficient of variation compared favorably with that of the standard method. In 123 normal women, the correlation coefficient (r) = .905. In menorrhagia cases, r = .901. In 20 VWD patients, r = .93. The CDC in-house method was compared to the BC Reagent method in 79 additional menorrhagia cases, with r = .94. The automated methods produced results equivalent or superior to those of traditional methods of measuring VWF:RCo.
authors.affiliation: Hematologic Diseases Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. crm5@cdc.gov
authors.forename: Connie H
authors.initials: CH
authors.lastname: Miller
authors.forename: S Jean
authors.initials: SJ
authors.lastname: Platt
authors.forename: Christine
authors.initials: C
authors.lastname: Daniele
authors.forename: Daniel
authors.initials: D
authors.lastname: Kaczor
mesh_terms: D001330:Electronic Data Processing; D005260:Female; D006801:Humans; D007202:Indicators and Reagents; D008595:Menorrhagia / Q000097:blood; D008722:Methods; D009391:Nephelometry and Turbidimetry / Q000295:instrumentation / Q000592:standards; D010974:Platelet Aggregation; D010979:Platelet Function Tests / Q000295:instrumentation / Q000592:standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014841:von Willebrand Factor / Q000032:analysis*
chemical_list: D007202:Indicators and Reagents; D014841:von Willebrand Factor