Background Careful assessment of bleeding history is the first step in the evaluation of patients with mild/moderate bleeding disorders, and the use of a bleeding assessment tool (BAT) is strongly encouraged. Although a few studies have assessed the utility of the ISTH‐BAT in patients with inherited platelet function disorders (IPFD) none of them was sufficiently large to draw conclusions and/or included appropriate control groups. Objectives The aim of the present study was to test the utility of the ISTH‐BAT in a large cohort of patients with a well‐defined diagnosis of inherited platelets disorder in comparison with two parallel cohorts, one of patients with type‐1 von Willebrand disease (VWD‐1) and one of healthy controls (HC). Patients/Methods We enrolled 1098 subjects, 482 of whom had inherited platelet disorders (196 IPFD and 286 inherited platelet number disorders [IT]) from 17 countries. Results IPFD patients had significantly higher bleeding score (BS; median 9) than VWD‐1 patients (median 5), a higher number of hemorrhagic symptoms (4 versus 3), and higher percentage of patients with clinically relevant symptoms (score > 2). The ISTH‐BAT showed excellent discrimination power between IPFD and HC (0.9 < area under the curve [AUC] < 1), moderate (0.7 < AUC < 0.9) between IPFD and VWD‐1 and between IPFD and inherited thrombocytopenia (IT), while it was inaccurate (AUC ≤ 0.7) in discriminating IT from HC. Conclusions The ISTH‐BAT allows to efficiently discriminate IPFD from HC, while it has lower accuracy in distinguishing IPFD from VWD‐1. Therefore, the ISTH‐BAT appears useful for identifying subjects requiring laboratory evaluation for a suspected IPFD once VWD is preliminarily excluded.

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La enfermedad de von Willebrand (VWD) es el desorden hemorrágico congénito más frecuente y se produce por la deficiencia y/o alteración del factor von Willebrand (VWF). El VWF es una glicoproteí-na multimérica que se sintetiza en las células endo-teliales y megacariocitos y se almacena en las orga-nelas de depósito: los cuerpos de Weibel Palade en las células endoteliales y los α-gránulos plaquetarios. Además, este factor circula en el plasma unido al factor VIII, protegiéndolo de la proteólisis mediada por inhibidores fisiológicos. La unidad funcional está conformada por un monómero, que luego dimeriza, a través de uniones S-S en el dominio VWF-CK, en el extremo C-terminal. Luego de sucesivos pasos de O- y N-glicosilación, se produce la unión de los dí-meros en multímeros, mediante uniones S-S entre el dominio VWF-D3. Los multímeros de VWF inclu-yen formas de peso molecular bajo (LMWM), inter-medio (IMWM), alto (HMWM) y formas de peso molecular ultragrandes (UHMWM). El VWF almacenado en las organelas de depósito y posteriormente liberado por la vía secretoria es rico en UHMWM, mientras que el VWF plasmático secretado constitutivamente presenta multímeros pequeños, intermedios y grandes. Los UHMWM son altamente trombogénicos y son degradados, una vez liberados, por la metaloproteasa plasmática ADAMTS13, en-zima que cliva específicamente al VWF entre los residuos Tyr1605-Met1606 localizados en el dominio VWF-A2.