The role of anemia on admission in acute coronary syndrome - An umbrella review of systematic reviews and meta-analyses

The role of erythrocytes in the acute coronary syndrome (ACS) is complex. The aim of this review in terms of PICO (P: patients; I: intervention; C: comparison; O: outcome) was to summarize systematic reviews in patients (P) with acute coronary syndrome, evaluating the effects of (I) 1) iron deficiency, 2) administration of an erythropoiesis-stimulating agent (ESA), 3) anemia on admission, 4) red blood cell transfusion, 5) a restrictive transfusion strategy in comparison (C) to 1) no iron deficiency, 2) no ESA 3) no anemia on admission, 4) no red blood cell transfusion, 5) a liberal transfusion strategy on mortality (O).We used AMSTAR2 to assess the methodological quality of systematic reviews and grade the available research. The primary endpoint was all-cause mortality.Using the data from 2,787,005 patients, the following conditions were associated with worse outcome in patients with ACS: anemia on admission (RR 2.08 95%CI 1.70-2.55) and transfusion (1.93 95%CI 1.12-3.34) of red blood cells. A liberal transfusion (RR 0.86 95%CI 0.70-1-05), administration of ESA (RR 0.55 95%CI 0.22-1.33) and iron deficiency (OR 1.24 95%CI 0.12-13.13) were not associated with altered all-cause mortality.Patients suffering from ACS and anemia on admission are at particular risk for adverse outcome. There is evidence of associations between adverse outcomes and receiving red blood cell transfusions.