title: [Is the incidence of parapneumonic pleural effusion increasing?].
abstract: BACKGROUND
  Streptococcus pneumoniae is the microorganism most frequently associated with complicated pleural effusion. After the introduction of the heptavalent pneumococcal vaccine, there was a decline in the incidence of invasive pneumococcal disease and, to a lesser extent, in that of pneumonia. However, the incidence of empyema apparently increased. The antipneumococcal heptavalent vaccine was introduced in Spain in 2001.
  
  
  OBJECTIVE
  To determine whether the incidence of pleural effusion secondary to pneumonia has increased in hospitalized patients and to examine the possible influence of the antipneumococcal heptavalent vaccine on the incidence rate of parapneumonic effusions.
  
  
  METHODS
  Patients aged less than 16 years old admitted to our hospital with a diagnosis of pneumonia between 1999 and 2005 were retrospectively reviewed. We calculated the annual incidence rate of pleural effusion with respect to the total number of patients admitted with pneumonia and with respect to patients considered to have probable bacterial pneumonia, based on previously established criteria.
  
  
  RESULTS
  A total of 337 patients were analyzed, of which 213 (63.2%) met the criteria for a diagnosis of probable bacterial pneumonia. Pleural effusion was found in 34 patients (15.9%), and 13 of these effusions (38%) were complicated. No clear trend was detected in the annual incidence of probable bacterial pneumonia per 100 admitted patients, although the highest numbers were detected in the last two years of the study period. The percentage of complications (effusions) remained constant (mean: 16.28%). No differences were found in the effusion rate between vaccinated and unvaccinated patients (12.5% vs 18.6%).
  
  
  CONCLUSIONS
  The trend in the incidence of parapneumonic pleural effusions was parallel and proportional to that of probable bacterial pneumonia.
authors.affiliation: Area de Pediatría y Neonatología, Fundación Hospital Alcorcón, Madrid, Spain. mbueno@fhalcorcon.es
authors.forename: M
authors.initials: M
authors.lastname: Bueno Campaña
authors.forename: B
authors.initials: B
authors.lastname: Agúndez Reigosa
authors.forename: S
authors.initials: S
authors.lastname: Jimeno Ruiz
authors.forename: F
authors.initials: F
authors.lastname: Echávarri Olavarría
authors.forename: M A
authors.initials: MA
authors.lastname: Martínez Granero
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D010996:Pleural Effusion / Q000453:epidemiology*; D012189:Retrospective Studies