Multicolor flow cytometry analysis performing classical manual gating revealed that although the numbers of circulating platelets (Figure S4A) were similar in FP-AS and SP-AS (Figure 4B), their activation status was significantly increased in FP-AS demonstrated by platelet CD62P+, CD41, and CD31 expression (CD62P; in percentage; median [IQR], 16.8 [11.58–23.8] versus 20.55 [12.48–32.28]; P=0.005), CD41 (3159 [1432–5816] versus 3949 [2567–5843]; P=0.03), CD31 (4087 [2918–5515] versus 5147 [3349–6733]; P<0.001; Figure 4B). The gene discussed is PECAM1; the disease is aortic stenosis.