The first use of a BAT in the description of the VWD bleeding phenotype was in the seminal International Multicenter Study (IMS), in which bleeding symptoms were collected in 42 obligatory carriers of type 1 VWD and compared with 215 control subjects; VWD obligatory carriers were studied to avoid any possible bias resulting from selection by symptom.18 In the study, each bleeding symptom received a score ranging from 0 (for absence) to 3. The gene discussed is VWF; the disease is von Willebrand disease (hereditary or acquired).