title: Thrombocytosis is a marker of poor outcome in community-acquired pneumonia.
abstract: BACKGROUND
  Thrombocytosis, often considered a marker of normal inflammatory reaction of infections, has been recently associated with increased mortality in hospitalized patients with community-acquired pneumonia (CAP). We assessed the characteristics and outcomes of patients with CAP and thrombocytosis (platelet count ≥ 4 × 105/mm3) compared with thrombocytopenia (platelet count &lt; 105/mm3) and normal platelet count.
  
  
  METHODS
  We prospectively analyzed 2,423 consecutive, hospitalized patients with CAP. We excluded patients with immunosuppression, neoplasm, active TB, or hematologic disease.
  
  
  RESULTS
  Fifty-three patients (2%) presented with thrombocytopenia, 204 (8%) with thrombocytosis, and 2,166 (90%) had normal platelet counts. Patients with thrombocytosis were younger (P &lt; .001); those with thrombocytopenia more frequently had chronic heart and liver disease (P &lt; .001 for both). Patients with thrombocytosis presented more frequently with respiratory complications, such as complicated pleural effusion and empyema (P &lt; .001), whereas those with thrombocytopenia presented more often with severe sepsis (P &lt; .001), septic shock (P = .009), need for invasive mechanical ventilation (P &lt; .001), and ICU admission (P = .011). Patients with thrombocytosis and patients with thrombocytopenia had longer hospital stays (P = .004), and higher 30-day mortality (P = .001) and readmission rates (P = .011) than those with normal platelet counts. Multivariate analysis confirmed a significant association between thrombocytosis and 30-day mortality (OR, 2.720; 95% CI, 1.589-4.657; P &lt; .001). Adding thrombocytosis to the confusion, respiratory rate, and BP plus age ≥65 years score slightly improved the accuracy to predict mortality (area under the receiver operating characteristic curve increased from 0.634 to 0.654, P = .049).
  
  
  CONCLUSIONS
  Thrombocytosis in patients with CAP is associated with poor outcome, complicated pleural effusion, and empyema. The presence of thrombocytosis in CAP should encourage ruling out respiratory complication and could be considered for severity evaluation.
authors.affiliation: Servei de Pneumologia, Institut del Torax, Hospital Clinic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Spain; Emergency Medicine Department, Istituto Di Ricovero e Cura a Carattere Scientifico Fondazione Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Prina
authors.affiliation: Servei de Pneumologia, Institut del Torax, Hospital Clinic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Spain; Centro de Investigación Biomedica En Red-Enfermedades Respiratorias (CibeRes, CB06/06/0028), Barcelona, Spain. Electronic address: Spainmiferrer@clinic.ub.es.
authors.forename: Miquel
authors.initials: M
authors.lastname: Ferrer
authors.affiliation: Servei de Pneumologia, Institut del Torax, Hospital Clinic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Spain; Respiratory Intensive Care Unit, Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo, Brazil.
authors.forename: Otavio T
authors.initials: OT
authors.lastname: Ranzani
authors.affiliation: Servei de Pneumologia, Institut del Torax, Hospital Clinic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Spain; Centro de Investigación Biomedica En Red-Enfermedades Respiratorias (CibeRes, CB06/06/0028), Barcelona, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Polverino
authors.affiliation: Servei de Pneumologia, Institut del Torax, Hospital Clinic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Spain; Centro de Investigación Biomedica En Red-Enfermedades Respiratorias (CibeRes, CB06/06/0028), Barcelona, Spain.
authors.forename: Catia
authors.initials: C
authors.lastname: Cillóniz
authors.affiliation: Servei de Pneumologia, Institut del Torax, Hospital Clinic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Spain; Centro de Investigación Biomedica En Red-Enfermedades Respiratorias (CibeRes, CB06/06/0028), Barcelona, Spain.
authors.forename: Encarnación
authors.initials: E
authors.lastname: Moreno
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Clínic, IDIBAPS, Barcelona, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Mensa
authors.affiliation: Servicio de Neumologia, Hospital Universitario La Fe, Valencia, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Montull
authors.affiliation: Centro de Investigación Biomedica En Red-Enfermedades Respiratorias (CibeRes, CB06/06/0028), Barcelona, Spain; Servicio de Neumologia, Hospital Universitario La Fe, Valencia, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Menéndez
authors.affiliation: Emergency Medicine Department, Istituto Di Ricovero e Cura a Carattere Scientifico Fondazione Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Cosentini
authors.affiliation: Servei de Pneumologia, Institut del Torax, Hospital Clinic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Spain; Centro de Investigación Biomedica En Red-Enfermedades Respiratorias (CibeRes, CB06/06/0028), Barcelona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Torres
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002116:Calcitonin / Q000097:blood; D017714:Community-Acquired Infections; D016207:Cytokines / Q000097:blood; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011014:Pneumonia / Q000097:blood / Q000150:complications* / Q000401:mortality*; D011446:Prospective Studies; D011498:Protein Precursors / Q000097:blood; D012372:ROC Curve; D012121:Respiration, Artificial; D013922:Thrombocytosis / Q000150:complications* / Q000401:mortality*; D016896:Treatment Outcome
chemical_list: D016207:Cytokines; D011498:Protein Precursors; D002116:Calcitonin