Diagnostic Performance of Von Willebrand Activity Versus Ristocetin Cofactor Tests in the Primary Evaluation of Von Willebrand Disease in Colombia

Background Accurate diagnosis of Von Willebrand Disease (VWD) is essential for effective management, but no single test can definitively confirm it due to the disease's complexity and the limitations of current methods. Tests measuring Von Willebrand Factor (VWF) binding activity, such as the platelet-dependent VWF activity test (VWF:Ab), have been developed, but their application in Latin American populations remains underexplored. This study aimed to evaluate the performance of the VWF:Ab test compared to the Ristocetin Cofactor test (VWF:GPIbR) in a Colombian population with suspected or confirmed VWD. Methods A diagnostic cross-sectional and retrospective study was conducted, including adults referred for hematological evaluation due to a personal or family history of bleeding disorders. Samples were analyzed using both VWF:GPIbR and VWF:Ab tests (HemosIL ® ) simultaneously. Diagnostic performance was assessed through sensitivity, specificity, predictive values. Additionally, correlation analyses were performed, and the level of agreement at various diagnostic thresholds was assessed. Results 125 patients were included, 88% of whom were women. A strong positive correlation was found between both tests (ICC = 0.96, p < 0.001). VWF:Ab had a specificity of 98.8% and sensitivity of 71.4%. Degree of agreement for 89.6% threshold was Normal (Greater than 50 IU/dL), Pathological (Less than 50.0 IU/dL). Notably, 7.2% of samples were classified as unclassifiable by VWF:Ab, highlighting potential limitations in qualitative defect detection Conclusion VWF:Ab exhibited high specificity and a strong correlation with VWF:GPIbR. Nevertheless, the differences in subtype classification and the identification of unclassifiable samples underscore the necessity of using both tests in a complementary manner.