Baseline platelet count and clinical outcome in acute coronary syndrome.

BACKGROUND It is unclear whether platelet count (PLT) is independently associated with clinical outcome in patients with acute coronary syndrome (ACS). METHODS AND RESULTS MEDLINE, EMBASE, the Cochrane library clinical trials registry, ISI Science Citation Index, and ISI Web of Knowledge were searched, supplemented by hand-scanning of references of relevant publications and contacting content experts. Eight studies including 39,324 patients were identified that addressed the following issues: major adverse cardiac events (MACE) and mortality were defined as endpoints; the relative risk (RR) or relative odds and their variance with MACE associated with PLT; studies in which only PLT was quantified. Two investigators independently abstracted information on study design, study and participant characteristics, PLT, clinical outcomes, control for potential confounding factors and risk estimates using a standardized protocol. At 1-month follow-up, compared with the bottom PLT group (< 150 × 10(9)/L), the pooled RRs of mortality and MACE were 1.78 (P=0.14) and 1.63 (P<0.001) for the upper PLT (> 350 × 10(9)/L), respectively. At long-term follow-up (≥ 1 year), the pooled RRs of mortality and MACE were 1.48 (P=0.02) and 1.28 (P=0.02) for the upper PLT, respectively. Moreover, the pooled RR of longitudinal mortality was 1.024 (P=0.03) when PLT was used as a continuous variable. CONCLUSIONS Higher PLT at baseline increases the RR of mortality and MACE in ACS patients.