title: Impact of routine systematic polymerase chain reaction testing on case finding for Legionnaires' disease: a pre-post comparison study.
abstract: BACKGROUND
  Legionnaires' disease cannot be clinically or radiographically distinguished from other causes of pneumonia, and specific tests are required to make the diagnosis. Currently, testing occurs erratically and, instead, clinicians rely on empiric treatment strategies and ignore public health implications of the diagnosis. We aimed to measure the increase in case detection of Legionnaires' disease following the introduction of routine polymerase chain reaction (PCR) testing of respiratory specimens. PCR is the most sensitive diagnostic tool for Legionnaires' disease.
  
  
  METHODS
  In a quasi-experimental study in Christchurch, New Zealand, we compared the number of cases of Legionnaires' disease requiring hospitalization diagnosed during a 2-year period before the introduction of a routine PCR testing strategy (November 2008-October 2010) with a similar period after the introduction (November 2010-October 2012). With this testing strategy, all respiratory specimens from hospitalized patients with pneumonia sent to the region's sole tertiary-level laboratory were tested for Legionella by PCR, whether requested or not.
  
  
  RESULTS
  During November 2008 to October 2010, there were 22 cases of Legionnaires' disease compared with 92 during November 2010 to October 2012. Of 1834 samples tested since November 2010, 1 in 20 was positive, increasing to 1 in 9 during peak Legionella season (November to January). Increasing bacterial load was associated with increasing disease severity.
  
  
  CONCLUSIONS
  In our region, the burden of Legionnaires' disease is much greater than was previously recognized. Routine PCR testing provides results within a clinically relevant time frame and enables improved characterization of the regional epidemiology of Legionnaires' disease.
authors.affiliation: Department of Pathology, University of Otago.
authors.forename: David R
authors.initials: DR
authors.lastname: Murdoch
authors.forename: Roslyn G
authors.initials: RG
authors.lastname: Podmore
authors.forename: Trevor P
authors.initials: TP
authors.lastname: Anderson
authors.forename: Kevin
authors.initials: K
authors.lastname: Barratt
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Maze
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: French
authors.forename: Sheryl A
authors.initials: SA
authors.lastname: Young
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Chambers
authors.forename: Anja M
authors.initials: AM
authors.lastname: Werno
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007875:Legionella / Q000235:genetics / Q000302:isolation & purification*; D007877:Legionnaires' Disease / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009520:New Zealand; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity
keywords: Legionella; Legionnaires’ disease; PCR; pneumonia