CRP and atrial fibrillation: Compared with patients with available ferritin on admission (380 of 447 patients [85.0%]), those without available ferritin (67 of 447 patients [15.0%]) were older and more likely to have coronary artery disease and atrial fibrillation and had shorter duration of symptoms, higher oxygen saturation on admission, and lower baseline C-reactive protein levels (eTable 1 in the Supplement).