title: Comparison of a new automated von Willebrand factor activity assay with an aggregation von Willebrand ristocetin cofactor activity assay for the diagnosis of von Willebrand disease.
abstract: von Willebrand disease (VWD) is caused by quantitative and/or qualitative defects of von Willebrand factor (VWF). The HemosIL von Willebrand Factor Activity assay, a new automated immunological test to measure VWF activity, was implemented on STAC and compared with the von Willebrand ristocetin cofactor activity (VWF:RCo) aggregation method. Imprecision and dilution studies were also performed. Within-run imprecision was 17.2% and between-run imprecision was 8.3% (coefficients of variation). Dilution studies showed a linearity between 12.5 and 100%. Passing and Bablok regression comparing the HemosIL von Willebrand Factor Activity assay and the aggregation method yielded a slope of 1.25 (95% confidence interval: 1.11-1.38) and intercept of -1.40 (95% confidence interval: -8.07 to 0.00). The correlation coefficient was 0.84 (95% confidence interval: 0.78-0.89). With a cut-off value of 50% for VWF activity, the assay has a sensitivity of 94.1% and a specificity of 92.8%, compared with the VWF:RCo aggregation assay with a cut-off value of 60% producing a sensitivity of 100.0% (specificity 87.6%). With a cut-off value of 60%, the HemosIL von Willebrand Factor Activity assay on STAC is a reliable assay for VWD. VWF:RCo or other functional testing is still required to confirm the diagnosis and for further classification of VWD.
authors.affiliation: Department of Clinical Chemistry, Microbiology and Immunology, Ghent University Hospital, Ghent, Belgium.
authors.forename: An
authors.initials: A
authors.lastname: De Vleeschauwer
authors.forename: Katrien
authors.initials: K
authors.lastname: Devreese
mesh_terms: D005260:Female; D006438:Hemodilution; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008297:Male; D012680:Sensitivity and Specificity; D014842:von Willebrand Diseases / Q000175:diagnosis*; D014841:von Willebrand Factor / Q000032:analysis* / Q000276:immunology
chemical_list: D014841:von Willebrand Factor