Comparison of type I, type III and type VI collagen binding assays in diagnosis of von Willebrand disease.

ABSTRACT

BACKGROUND: von Willebrand factor (VWF) plays a key role in coagulation by tethering platelets to injured subendothelium through binding sites for collagen and platelet GPIb. Collagen binding assays (VWFCB), however, are not part of the routine work-up for von Willebrand disease (VWD). OBJECTIVES: This study presents data on collagen binding for healthy controls and VWD subjects to compare three different collagens. PATIENTS/METHODS: VWF antigen (VWFAg), VWF ristocetin cofactor activity and VWFCB with types I, III and VI collagen were examined for samples obtained from the Zimmerman Program. RESULTS: Mean VWFCB in healthy controls was similar and highly correlated for types I, III and VI collagen. The mean VWFCB/VWFAg ratios for types I, III and VI collagen were 1.31, 1.19 and 1.21, respectively. In type 1 VWD subjects, VWFCB was similar to VWFAg with mean VWFCB/VWFAg ratios for types I, III and VI collagen of 1.32, 1.08 and 1.1, respectively. For type 2A and 2B subjects, VWFCB was uniformly low, with mean ratios of 0.62 and 0.7 for type I collagen, 0.38 and 0.4 for type III collagen, and 0.5 and 0.47 for type VI collagen. CONCLUSIONS: Normal ranges for type I, III and VI collagen are correlated, but higher values were obtained with type I collagen as compared with types III and VI. The low VWFCB in type 2A and 2B subjects suggests that VWFCB may also supplement analysis of multimer distribution. However, these results reflect only one set of assay conditions per collagen type and therefore may not be generalizable to all collagen assays.