A call to action for the use of composite hematologic measurements in hereditary hemorrhagic telangiectasia and other chronic bleeding disorders

INTRODUCTION: Therapeutic development in hereditary hemorrhagic telangiectasia (HHT), the second-most-common inherited bleeding disorder, is rapidly accelerating. Therefore, modern clinical trials in HHT must be equipped with rigorous, fit-for-purpose endpoints. AREAS COVERED: Due to the inadequacy of solitary hematologic measurements (hemoglobin, red cell transfusions and quantity of iron infused used as separate measurements), the recent International Consensus Report on Standardization in HHT advised widespread implementation of two composite hematologic measurements, the Hematologic Support Score and Hematologic Impact Score. The Hematologic Support Score is a composite measurement of total hematologic support (red cell transfusions and quantity of iron infused) administered over a time period, and the Hematologic Impact Score provides the total hematologic impact of an intervention, in red-cell unit equivalents, by integrating change in hemoglobin, red cell transfusions, and quantity of iron infused. EXPERT OPINION: This article, authored by 16 hematologist-experts in HHT, hemostasis, and iron deficiency, explains these measures in depth and the importance of their implementation in clinical studies of major disorders of chronic bleeding, such as HHT, gastrointestinal angiodysplasia, and heavy menstrual bleeding. We urge clinicians, investigators, study sponsors and regulatory bodies to adopt and promote the use of these common-sense measurements in clinical studies of chronic bleeding interventions.