A Comparative Evaluation of an Automated Functional Assay for Von Willebrand Factor Activity in Type 1 Von Willebrand Disease

Shiue-Wei Lai,1– 3 Chia-Yau Chang,3,4 Shin-Nan Cheng,1,5,6 Shu-Hsia Hu,1 Chung-Yu Lai,7 Yeu-Chin Chen1,2 1Hemophilia Care and Research Center, Tri-Service General Hospital, Taipei, Taiwan; 2Division of Hematology/Oncology, Department of Internal Medicine, Tri-service General Hospital, National Defense Medical Center, Taipei, Taiwan; 3School of Medicine, Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan; 4Division of Pediatric Hematology/Oncology, Hemophilia Center, Taipei Medical University Hospital, Taipei, Taiwan; 5Department of Pediatrics, Tungs’ Taichung MetroHarbor Hospital, Taichung, Taiwan; 6Department of Pediatrics, National Defense Medical Center, Taipei, Taiwan; 7Graduate Institute of Aerospace and Undersea Medicine, National Defense Medical Center, Taipei City, 114, TaiwanCorrespondence: Yeu-Chin ChenDivision of Hematology/Oncology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Chenggong Road, Neihu, Taipei, 114, TaiwanTel +886-2-87927208Fax +888-2-87927209Email yeuchin99@gmail.comBackground: von Willebrand factor ristocetin cofactor activity (VWF:RCo) is the standard functional assay used for von Willebrand disease (VWD) diagnosis. However, it has some drawbacks including being time consuming and labor intensive and having high inter-laboratory variability. The HemosIL VWF activity assay has the advantages of both high speed and automation. The purpose of this study was to prospectively compare these two functional assays for type 1 VWD detection.Methods: Plasma samples from 108 subjects were assessed in this study. HemosIL VWF activity was measured with the HemosIL latex immunoturbidimetric commercial kits by the ACL TOP coagulation analyzer. VWF:RCo was measured by platelet aggregation method. Pearson correlation analyses were performed to estimate the correlation of HemosIL VWF activity with VWF:RCo. Receiver-operator characteristic (ROC) curve analysis was used to evaluate the performance of the two diagnostic tests.Results: The correlation coefficient between VWF:RCo and HemosIL VWF activity was 0.874 overall and was 0.761 and 0.811 in the cohorts of type 1 VWD and non-VWD, respectively. The sensitivity and specificity of HemosIL VWF activity assay for type 1 VWD identification were 94.7% and 80.0%, respectively, and the ROC curve of HemosIL VWF activity was larger than that of VWF:RCo (0.928 vs 0.863, p=0.0138). Finally, the positive and negative predictive values of the HemosIL VWF activity assay for type 1 VWD detection were 72.0% and 96.6%, respectively.Conclusion: Our results demonstrate that the HemosIL VWF activity assay was an effective method for type 1 VWD screening and diagnosis. It carried good sensitivity and specificity and had a higher ROC curve than VWF:RCo besides showing good correlation with VWF:RCo. With its advantages of greater speed and automated performance, these results suggest that the HemosIL VWF activity assay was reliable and precise in the clinical setting.Keywords: von Willebrand factor antigen, von Willebrand disease, VWF ristocetin cofactor activity, VWF:RCo, HemosIL VWF activit