PF4 and atrial fibrillation: Mean platelet volume (MPV), circulating levels of platelet factor-4 (PF-4), β-thromboglobulin (BTG) and P-selectin were higher in AF cases than controls, with a pooled SMD of 0.92 (95% CI, 0.12–1.73; P = 0.025), 1.72 (95% CI, 0.96–2.49; P<0.001), 1.61 (95% CI, 1.03–2.19; P<0.001), and 0.50 (95% CI, 0.23–0.77; P<0.001), respectively (Fig 2B–2E).