A new study suggests that for evaluating von Willebrand factor (VWF) ristocetin cofactor activity (RCo), the HemosIL VWF activity assay is fast, reliable, and precise with use in the clinical setting for identification of type 1 von Willebrand disease (VWD). The results of the study were published in the International Journal of General Medicine.

“VWF:RCo activity has been the mainstay of functional testing for type 1 VWD,” the researchers wrote in their report. However, the analysis can be difficult to perform and with a high degree of variability across laboratories. The HemosIL VWF activity assay offers a high-throughput approach to VWF measurement, the researchers explained in their report.

In this prospective study, the researchers evaluated plasma samples obtained from a total of 108 individuals to compare 2 VWF analysis techniques used in diagnosis of VWD. These included a VWF:RCo assay based on a platelet aggregation method, which served as a reference method in comparison to the HemosIL VWF activity assay for screening and diagnosis of type 1 VWD. The HemosIL VWF activity assay involves detection of turbidity that results from the agglutination that occurs when VWF interacts with latex particles coated in antibodies directed at the glycoprotein Ib receptor of VWF.

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From the study population, 38 individuals were patients with type 1 VWD, and 70 individuals formed a cohort without VWD. Patients in the VWD cohort had a mean age of 35.4 years, compared with 29.3 years for the non-VWD cohort (P =.033).

Results from the VWF:RCo assay and the HemosIL VWF activity assay showed a correlation coefficient of 0.874 for the overall population. For the VWD cohort, the correlation coefficient for results from these 2 assays was 0.761, and it was 0.811 for the non-VWD cohort. In detection of type 1 VWD, the positive predictive value was 72.0% with the HemosIL VWF activity assay, the negative predictive value for this assay was 96.6%, and its accuracy was 82.4%. This assay also showed a sensitivity of 94.7% and specificity of 80.0% for detection of type 1 VWD in receiver operating characteristic (ROC) curve analysis.

Numerically the HemosIL VWF activity assay showed higher values for specificity, positive predictive value, negative predictive value, and accuracy, but the differences between assays were reportedly not significant for these values. However, the areas under the curve in ROC curve analysis were significantly different. These values were 0.928 for the HemosIL VWF activity assay and 0.863 for the VWF:RCo approach (P =.0138).

The researchers concluded that the performance of each assay showed a high degree of correlation and suggested the HemosIL VWF activity assay was sensitive, fast, and cost-effective. “Taken together, we believe the results of our analyses provide valuable practical guidance to clinicians who care for this population,” the researchers concluded in their report.


Lai SW, Chang CY, Cheng SN, Hu SH, Lai CY, Chen YC. A comparative evaluation of an automated functional assay for von Willebrand factor activity in type 1 von Willebrand disease. Int J Gen Med. 2021;14:5167-5174. doi:10.2147/IJGM.S321605