title: Thrombocytopenia in Staphylococcus aureus bacteremia: risk factors and prognostic importance.
abstract: OBJECTIVE
  To identify risk factors and outcomes associated with thrombocytopenia at sepsis onset in Staphylococcus aureus bacteremia.
  
  
  METHODS
  This single-center, retrospective, cohort study consists of all adult patients with a first episode of clinical S aureus bacteremia between April 1, 1988, and September 30, 1994, and between January 1, 1999, and December 31, 2007. Thrombocytopenia was defined as a platelet count less than 150 × 10(9)/L. The primary outcome was 30-day all-cause mortality. Risk factors for 30-day all-cause mortality were identified using univariate and multivariable analyses. Multivariable analysis was conducted using forward step logistic regression analysis. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for risk of death.
  
  
  RESULTS
  A total of 1052 patients had clinical S aureus bacteremia. Thrombocytopenia at sepsis onset was present in 235 patients (22.3%). Thrombocytopenia was associated with community-acquired bacteremia, infections caused by methicillin-sensitive S aureus, high-magnitude bacteremia (defined as >4 positive blood cultures [≥ 3 separate positive blood culture sets]), and endocarditis. Patients with thrombocytopenia presented more commonly with severe sepsis reflected by septic shock and acute renal failure. Thirty-day mortality was significantly higher among patients with thrombocytopenia (132/235 [56.2%]) vs those without thrombocytopenia (281/817 [34.4%]; P<.001). Higher mortality was associated with the degree of thrombocytopenia. In multivariable analysis, thrombocytopenia at baseline remained an independent risk factor for 30-day mortality (OR, 2.82; 95% CI, 1.87-4.24). The adjusted association between thrombocytopenia and death remained similar among the 917 patients with monomicrobial bacteremia (OR, 2.88; 95% CI, 1.83-4.53) and the 945 patients who did not die within the first 48 hours (OR, 2.88; 95% CI, 1.87-4.45.).
  
  
  CONCLUSIONS
  We observed a strong association between thrombocytopenia at sepsis onset and all-cause mortality in S aureus bacteremia, possibly related to mechanisms other than sepsis alone.
authors.affiliation: Department of Medicine E, Rabin Medical Center, Beilinson Hospital, Petah-Tikva 49100, Israel. anatga2@clalit.org.il
authors.forename: Anat
authors.initials: A
authors.lastname: Gafter-Gvili
authors.forename: Nariman
authors.initials: N
authors.lastname: Mansur
authors.forename: Assaf
authors.initials: A
authors.lastname: Bivas
authors.forename: Noa
authors.initials: N
authors.lastname: Zemer-Wassercug
authors.forename: Jihad
authors.initials: J
authors.lastname: Bishara
authors.forename: Leonard
authors.initials: L
authors.lastname: Leibovici
authors.forename: Mical
authors.initials: M
authors.lastname: Paul
mesh_terms: D000368:Aged; D019540:Area Under Curve; D016470:Bacteremia / Q000150:complications* / Q000401:mortality*; D002423:Cause of Death; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D010976:Platelet Count; D011379:Prognosis; D012372:ROC Curve; D012189:Retrospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000150:complications* / Q000401:mortality*; D013211:Staphylococcus aureus; D013921:Thrombocytopenia / Q000150:complications* / Q000401:mortality*