Collagen-Binding Assay Assessed for Bleeding Disorder

As there are different types of VWD, no single test is sufficient for diagnosis, so testing of both von Willebrand factor (VWF) antigen and function must be performed, and one assay yielded more favorable discrimination of type 1 and 2 VWD.

Scientists at Westmead Hospital, (Westmead, NSW, Australia) tested plasma samples from 52 type I and 49 type 2 VWD patients and 242 plasma samples from apparently healthy individuals to determine the normal reference interval. Precision analysis was performed using three reference plasma samples. A collagen-binding enzyme-linked immunosorbent assay (ELISA) was performed and the absorbance was read at 450 nm with a 650 nm reference on a Versamax plate reader (Molecular Devices, Sunnyvale, CA, USA). Values of controls and samples were obtained through extrapolation from a reference curve.

Repeatability and within-laboratory precision studies of the ELISAcheck Collagen Binding Assay (Precision BioLogic; Halifax, NS, Canada) resulted in coefficients of variation of less than 11%. A linear range of 0.01-3.54 IU/mL was determined, along with a limit of detection of 0.016 IU/mL and a lower limit of quantitation of 0.04 IU/mL. Samples tested from apparently healthy individuals resulted in a normal range of 0.54-2.17 IU/mL. The known VWD type 1 and type 2 samples were also analyzed by the ELISA, with 99% of samples having VWF:collagen binding below the normal reference range and an estimated 96% sensitivity and 87% specificity using a VWF collagen-binding/antigen cutoff ratio of 0.50.

The authors concluded that the VWF:collagen binding ELISA provides an accurate measure of collagen-binding activity that aids in the diagnosis and differentiation of type 1 from type 2 VWD. Although proper identification and typing of VWD requires a panel of assays to allow the best patient care and therapeutic management, the ELISAcheck Collagen Binding Assay is a valuable addition to the current VWD diagnostic toolbox. The study was published in the April 2013 issue of the International Journal of Laboratory Hematology.

Related Links:
Westmead Hospital
Molecular Devices
Precision BioLogic