title: Ruling out Legionella in community-acquired pneumonia.
abstract: BACKGROUND
  Assessing the likelihood for Legionella sp. in community-acquired pneumonia is important because of differences in treatment regimens. Currently used antigen tests and culture have limited sensitivity with important time delays, making empirical broad-spectrum coverage necessary. Therefore, a score with 6 variables recently has been proposed. We sought to validate these parameters in an independent cohort.
  
  
  METHODS
  We analyzed adult patients with community-acquired pneumonia from a large multinational database (Community Acquired Pneumonia Organization) who were treated between 2001 and 2012 with more than 4 of the 6 prespecified clinical variables available. Association and discrimination were assessed using logistic regression analysis and area under the curve (AUC).
  
  
  RESULTS
  Of 1939 included patients, the infectious cause was known in 594 (28.9%), including Streptococcus pneumoniae in 264 (13.6%) and Legionella sp. in 37 (1.9%). The proposed clinical predictors fever, cough, hyponatremia, lactate dehydrogenase, C-reactive protein, and platelet count were all associated or tended to be associated with Legionella cause. A logistic regression analysis including all these predictors showed excellent discrimination with an AUC of 0.91 (95% confidence interval, 0.87-0.94). The original dichotomized score showed good discrimination (AUC, 0.73; 95% confidence interval, 0.65-0.81) and a high negative predictive value of 99% for patients with less than 2 parameters present.
  
  
  CONCLUSIONS
  With the use of a large independent patient sample from an international database, this analysis validates previously proposed clinical variables to accurately rule out Legionella sp., which may help to optimize initial empiric therapy.
authors.affiliation: Kantonsspital Aarau, Medical University Clinic, Aarau, Switzerland; University Clinic of Infectious Diseases, University Hospital, Inselspital Bern, Bern, Switzerland. Electronic address: sebastian.haubitz@gmail.com.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Haubitz
authors.affiliation: University of Basel, Basel, Switzerland.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Hitz
authors.affiliation: University of Basel, Basel, Switzerland.
authors.forename: Lena
authors.initials: L
authors.lastname: Graedel
authors.affiliation: Kantonsspital Aarau, Medical University Clinic, Aarau, Switzerland.
authors.forename: Marcus
authors.initials: M
authors.lastname: Batschwaroff
authors.affiliation: Division of Infectious Diseases, University of Louisville School of Medicine, Louisville, Ky.
authors.forename: Timothy Lee
authors.initials: TL
authors.lastname: Wiemken
authors.affiliation: Division of Infectious Diseases, University of Louisville School of Medicine, Louisville, Ky.
authors.forename: Paula
authors.initials: P
authors.lastname: Peyrani
authors.affiliation: Division of Infectious Diseases, University of Louisville School of Medicine, Louisville, Ky.
authors.forename: Julio A
authors.initials: JA
authors.lastname: Ramirez
authors.affiliation: Kantonsspital Aarau, Medical University Clinic, Aarau, Switzerland; Kantonsspital Aarau, Clinic for Infectious Diseases, Aarau, Switzerland.
authors.forename: Christoph Andreas
authors.initials: CA
authors.lastname: Fux
authors.affiliation: Kantonsspital Aarau, Medical University Clinic, Aarau, Switzerland.
authors.forename: Beat
authors.initials: B
authors.lastname: Mueller
authors.affiliation: Kantonsspital Aarau, Medical University Clinic, Aarau, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Schuetz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002097:C-Reactive Protein / Q000032:analysis; D017714:Community-Acquired Infections / Q000097:blood / Q000188:drug therapy / Q000382:microbiology*; D003371:Cough; D016208:Databases, Factual; D003657:Decision Making; D005060:Europe; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000097:blood; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D016952:Legionella pneumophila / Q000187:drug effects / Q000302:isolation & purification*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D009656:North America; D010976:Platelet Count; D018410:Pneumonia, Bacterial / Q000097:blood / Q000188:drug therapy / Q000382:microbiology*; D011237:Predictive Value of Tests; D013020:South America; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D002097:C-Reactive Protein; D007770:L-Lactate Dehydrogenase
keywords: Legionella; Pneumonia; Prediction algorithm