Plasma von Willebrand factor antigen concentration as a predictor of von Willebrand's disease status in German Wirehaired Pointers

Objective-To evaluate the use of plasma von Willebrand's factor (vWF) concentration as a screening test for inherited von Willebrand's disease (vWD) in German Wirehaired Pointers (GWHP). Design-Prospective study. Sample Population-Plasma samples from 467 GWHP. Procedure-Plasma VWF concentrations were measured as vWF antigen (vWF:Ag), using ELISA, and test values were used to estimate prevalence of vWD in GWHP and predict parental vWD status. Test results of progeny from matings of carrier and noncarrier parents were then compared with the predicted outcome of such matings. Results-376 (81%) GWHP were classified as vWD noncarriers, 58 (12%) as carriers, and 5 (1%) as affected with vWD. An additional 28 (6%) GWHP could not be classified on the basis of plasma vWF:Ag concentration. The observed outcome of tests of 213 pups was not significantly different from that predicted on the basis of parental vWF:Ag concentration. The predictive value of a positive test result (VWF: Ag% < 50) for identifying vWD carriers was 0.89. Clinical Implications-Plasma vWF:Ag concentration was an effective predictor of genetic status for the vWD trait, and for the outcome of matings between carriers and noncarriers of vWD in this study of GWHP.