title: Incidence and prognostic significance of thrombocytopenia developed during acute coronary syndrome in contemporary clinical practice.
abstract: BACKGROUND
  Prior studies examining thrombocytopenia among patients with acute coronary syndromes (ACS) evaluated highly selected patients in a clinical trial setting using varying definitions of thrombocytopenia. The incidence, severity, and prognostic significance of acquired thrombocytopenia during ACS in community practice have not been well defined.
  
  
  RESULTS
  We examined 36 182 patients with non-ST-segment elevation ACS enrolled at 379 US hospitals participating in the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes With Early Implementation of the American College of Cardiology/American Heart Association Guidelines (CRUSADE) quality improvement initiative between June 2004 and December 2006. Patients with baseline platelet counts <150x10(9)/L were excluded. Overall, 4697 patients (13%) developed new thrombocytopenia, defined as nadir platelet count <150x10(9)/L (referenced lower limit of normal), during their ACS hospitalization. Risks of in-hospital mortality and bleeding correlated directly with severity of thrombocytopenia; even mild thrombocytopenia (nadir 100 to 149x10(9)/L) was associated with increased risks of mortality (adjusted odds ratio [OR], 2.01; 95% CI, 1.69 to 2.38) and bleeding (adjusted OR, 3.76; 95% CI, 3.43 to 4.12). Each 10% drop in platelet count was associated with increased mortality and bleeding risks (adjusted ORs, 1.39 [95% CI, 1.33 to 1.46] and 1.89 [95% CI, 1.83 to 1.95], respectively). A >/=50% drop in platelet count was associated with higher risk of adverse outcomes regardless of the nadir count. A novel combined definition of acquired thrombocytopenia-nadir <150x10(9)/L or platelet count drop >or=50%-identifies a population of ACS patients at higher risk of mortality and major bleeding (adjusted ORs, 2.58 [95% CI, 2.23 to 2.98] and 4.32 [95% CI, 3.97 to 4.70], respectively).
  
  
  CONCLUSIONS
  Thrombocytopenia, a common complication of ACS, is associated with increased mortality and bleeding risks. Even mild thrombocytopenia or a platelet count drop >/=50% in the setting of normal nadir values is clinically significant. Application of a combined definition for thrombocytopenia using both absolute and relative thresholds permits increased sensitivity for patients at high risk of adverse outcomes.
authors.affiliation: Duke Clinical Research Institute, Terrace Level, Durham, NC 27705, USA. wang0085@mc.duke.edu
authors.forename: Tracy Y
authors.initials: TY
authors.lastname: Wang
authors.forename: Fang-Shu
authors.initials: FS
authors.lastname: Ou
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Roe
authors.forename: Robert A
authors.initials: RA
authors.lastname: Harrington
authors.forename: E Magnus
authors.initials: EM
authors.lastname: Ohman
authors.forename: W Brian
authors.initials: WB
authors.lastname: Gibler
authors.forename: Eric D
authors.initials: ED
authors.lastname: Peterson
mesh_terms: D054058:Acute Coronary Syndrome / Q000401:mortality*; D000368:Aged; D000369:Aged, 80 and over; D000789:Angina, Unstable / Q000401:mortality; D000925:Anticoagulants / Q000627:therapeutic use*; D001241:Aspirin / Q000627:therapeutic use; D000077144:Clopidogrel; D005260:Female; D006470:Hemorrhage / Q000401:mortality*; D006493:Heparin / Q000627:therapeutic use*; D006801:Humans; D015994:Incidence; D007297:Inpatients / Q000706:statistics & numerical data; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use; D010976:Platelet Count; D011379:Prognosis; D012042:Registries; D012307:Risk Factors; D012720:Severity of Illness Index; D013921:Thrombocytopenia / Q000188:drug therapy* / Q000401:mortality*; D013988:Ticlopidine / Q000031:analogs & derivatives / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D010975:Platelet Aggregation Inhibitors; D006493:Heparin; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin