The assessment gap in PV. Clinical trial endpoints such as hematocrit (Hct) control, splenomegaly, symptoms/quality of life (QOL), and JAK2 V617F allele burden are shorter-term clinical trial endpoints for which higher-level evidence has been obtained with randomized trials evaluating aspirin/phlebotomy, hydroxyurea (HU), ruxolitinib (RUX), and pegylated interferons (IFNs). However, endpoints with lower-event rates (eg, thrombosis) or longer-horizon outcomes such as evolution to myelofibrosis (MF) and acute myeloid leukemia (AML), and survival cannot be readily assessed within the timeframe of such trials. Therefore, bridging this data divide in the setting of a chronic myeloid neoplasm such as PV requires reliance on aggregate data from surrogate studies (eg, large retrospective and real-world observational studies and registry analyses). Professional illustration by Ian Baker; figure conceived by J.G.