Summary
Von Willebrand disease (VWD) is the most common bleeding disorder, but no bedside
tests specific for Von Willebrand factor are available. The objective of this study
was to evaluate the diagnostic accuracy of whole blood ristocetin-induced platelet
aggregometry (WB-RIPA) in VWD. WB-RIPA was performed in VWD patients (n=100) and healthy
controls (n=17) using the Multiplate® platelet impedance aggregometry platform. The
diagnostic properties of the test were described as sensitivity/specificity, positive
and negative predictive value, and ROC area under the curve (AUC). Patients with VWD
had impaired platelet aggregation by WB-RIPA. At a cut-off of 98 U, the test sensitivity
and specificity of WB-RIPA for VWD was 0.95 and 0.53. A cut-off of 60 U provided a
specificity of 1.00 with reduced sensitivity of 0.76. All patients with type 3 VWD
and >90% of patients with type 2 VWD were accurately distinguished from the controls.
Incorrect classifications were attributable to patients with type 1 VWD, showing partly
overlapping WB-RIPA results with healthy controls. Remarkably, these patients had
lower bleeding scores and higher VWF activity than other type 1 VWD patients. Overall,
WB-RIPA discriminated VWD patients from healthy controls accurately with a ROC AUC
of 0.94. These results show that WB-RIPA is a promising diagnostic test for VWD, especially
when timely results are required. Depending on the chosen test threshold, WB-RIPA
could be clinically used as a rule out test, or to suggest patients in whom further
testing for VWD is warranted.
Keywords
Von Willebrand disease - Ristocetin induced platelet aggregometry - Multiplate - Whole
blood impedance platelet aggregometry
