Two recent large retrospective studies incorporating the data of over 10 years of experience confirmed the high diagnostic value of PFA-100 in detecting VWD.43, 52Normal PFA-100 results are especially rare in patients with abnormal VWF function or a lower quantity of large molecular VWF multimers.24, 26, 32, 35, 60, 78, 80, 81In cases of mild type 1 VWD the false-negative rate is higher. This evidence concerns the gene VWF and von Willebrand disease 1.