title: Optimization of the automated, CS-2000i™ method for measuring low levels of von Willebrand factor ristocetin cofactor activity (VWF:RCo).
abstract: Measurements of von Willebrand factor ristocetin cofactor activity (VWF:RCo) are necessary for the diagnosis of von Willebrand disease (VWD). However, the conventional manual glass-plate method is technically demanding, and exhibits high intra-/inter-laboratory variation. An automated technique has been recently described utilizing the CS-2000i™ with specific VWF:RCo reagents, but measurements at lower levels (<10 IU/dL) lack reliability. We have optimized this automated system for measuring low levels of VWF:RCo. Using a sample volume (72 μL) and initial stirring speed (400 rpm), the lowest level of VWF:RCo detected with a CV < 20 % was 2.5 IU/dL. Greater variability was evident at this stirring speed with smaller sample volumes. Decreasing the stirring speed (200 rpm) with a sample volume (72 μL), however, significantly improved the CV, and enabled measurements at the lowest levels (≤2.5 IU/dL). The optimized assay demonstrated a high correlation (R(2) = 0.841) with the glass-plate method at <10 IU/dL VWF:RCo, suggesting that the different VWF:RCo reagents did not affect the results. In addition, changes in VWF:RCo post-DDAVP infusions were parallel in both assays, indicating that the automated method is suitable for the clinical monitoring of treatment in VWD. The optimized automated measurement of VWF:RCo offers a promising method for evaluating VWF at low levels of hemostatic activity.
authors.affiliation: Department of Pediatrics, Nara Medical University, 840 Shijo-cho, Kashihara, Nara, 634-8522, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Keiji
authors.initials: K
authors.lastname: Nogami
authors.forename: Masahiro
authors.initials: M
authors.lastname: Okuda
authors.forename: Midori
authors.initials: M
authors.lastname: Shima
mesh_terms: D057205:Automation, Laboratory; D001779:Blood Coagulation Factors; D001780:Blood Coagulation Tests / Q000379:methods* / Q000592:standards*; D006801:Humans; D015203:Reproducibility of Results; D014842:von Willebrand Diseases / Q000097:blood* / Q000175:diagnosis*; D014841:von Willebrand Factor
chemical_list: D001779:Blood Coagulation Factors; D014841:von Willebrand Factor