Evaluation of the von Willebrand factor antigen (vWF-Ag) assay using an immuno-turbidimetric method (STA Liatest vWF) automated on the MDA 180 coagulometer.

The standard enzyme-linked immunosorbent assay (ELISA) test for von Willebrand factor antigen (vWF-Ag), though sensitive and specific, does not deliver the flexibility to handle single sample assessments economically or provide rapid, emergency testing capability. The present study examined the performance characteristics of an immuno-turbidimetric assay kit (STA Liatest) modified for automation on the MDA(R)180 coagulation analyser using a supplied protocol. One hundred and sixteen patient samples were assessed by both the standard and the modified method. The correlation coefficient was 0.98 across the range of values 1-487 IU/dl. Above 200 IU/dl, where specimen dilution was indicated, there was greater diversity (r = 0.86) between the techniques. Plotting the difference between methods against the mean of both showed excellent agreement between methods below 100 IU/dl vWF. The intra-assay and interassay coefficients of variation were less than 3% at both low and normal range levels. The MDA(R)180 automated vWF assay merits consideration as an alternative to ELISA testing that provides random access and result availability within 30 min.