Comparison of the Siemens vWF:RCo and the Instrumentation Laboratory HaemosIL von Willebrand Factor Activity Assays for the Diagnosis of Von Willebrand Disease

Von Willebrand disease is a bleeding disorder caused either by a quantitative or a qualitative abnormality in the plasma protein, von Willebrand factor. The diagnosis and classification of von Willebrand disease relies upon a panel of screening and confirmatory laboratory tests. In this study the Siemens von Willebrand factor ristocetin cofactor assay was used to test 59 patient samples submitted to Waikato Hospital Laboratory. The samples were also tested using the Instrumentation Laboratory HaemosIL von Willebrand Factor activity assay which is a potential replacement for the Siemens assay. The two assays showed good correlation of results below the 80% level. The HaemosIL assay showed better intra-batch precision, however, inter-batch precision revealed little difference between the two assays. The Siemens assay was more time consuming to perform, however, reagent costs were lower than the HaemosIL assay. This study demonstrated that the HaemosIL assay could be useful in the laboratory investigation of von Willebrand disease. Whether it is a suitable replacement for the von Willebrand factor ristocetin cofactor assay remains unanswered. The lack of sufficient samples with low von Willebrand factor and the unavailability of samples from von Willebrand types and subtypes did not allow for a complete evaluation of the performance of the HaemosIL assay in this study.