WM platelets have altered thrombopoietic and age-related phenotypic markers. (A) Platelet count, (B) mean platelet volume (MPV), (C) serum thrombopoietin (TPO), (D) normalized thiazole orange (TO) staining of platelets in WB (divided by HD mean), (E) relative proportion of TO^bright WM platelets falling within the gate encompassing the top 10% of HD platelets (log₁₀ WM/HD %), (F) platelet surface receptor levels in PRP and (G) sGPVI levels in platelet-poor plasma (PPP) from HDs (n = 9-15, blue), patients with WM not on therapy (n = 9-13, red), or receiving BTKis (n = 0-5, green). For panels A-C,E,G, mean +/± SD. For panels D,F, normalized geomeans (divided by mean HD geomean) ± standard error of the mean (SEM). For panels A-C, P values were determined by Kruskal-Wallis 1-way analysis of variance (ANOVA) with Dunn's multiple comparisons test, performed on the raw data; for panel E, Mann-Whitney t test; or for panel E, 1 sample t test.