VWF and von Willebrand disease (hereditary or acquired): In 2 students, vWF:RCo exhibited values close to limits like 45%, but evaluation of the blood groups revealed no individuals with blood group O. In vWD, the vWF:RCo value is regarded as the gold standard diagnostic method; therefore, 14 of the 40 suspected patient (4 males, 10 females) were determined to have type-1 vWD.