The ISTH Bleeding Assessment Tool (ISTH-BAT) was developed in 2010 by the Scientific and Standardisation Committee (SSC) of the International Society on Thrombosis and Haemostasis to provide a standardised, validated instrument for quantifying bleeding history in patients suspected of having inherited bleeding disorders. Before the ISTH-BAT, at least five different bleeding questionnaires were in use, making it impossible to compare data across centres and studies. The ISTH-BAT assigns severity scores (0-4) for each of 14 bleeding symptoms and calculates a total bleeding score (BS). An abnormal BS (>3 in males or >5 in females) has been validated as predictive of von Willebrand disease, platelet function disorders, and other inherited bleeding conditions.