Incidence, Etiology, and Outcomes of Community-Acquired Pneumonia: A Population-Based Study

Bjarnason, Agnar; Westin, Johan; Lindh, Magnus; Andersson, Lars-Magnus; Kristinsson, Karl G; Löve, Arthur; Baldursson, Olafur; Gottfredsson, Magnus

Several studies have been published over the last decade utilizing nucleic acid amplification techniques to assess the etiology of pneumonia. A recent prospective study from the United States demonstrated that S pneumoniae accounted for 5% of pneumonia requiring admission compared with 20% in this study. A possible explanation may be that Jain et al [12] recovered high-quality sputum samples from only 12% of their participants compared with 31% in this study. Another contributing factor may be more widespread vaccination with the conjugated pneumococcal vaccine in the US population, which had not been introduced in Iceland when this study was performed. Another, smaller study set in the United States found S pneumoniae in 19% of their cohort, which is similar to our results [10] . From Europe, Holter et al [11] recently recovered pneumococci in 30% of admitted CAP patients in Norway where conjugated pneumococcal vaccine is included in the childhood vaccination program. Also of note, if results from nasopharyngeal culture and upper airway PCR are omitted, the rate was 18% [11] . Similarly, Bonten et al [24] found that 21% of CAP cases among those >65 years of age were due to S pneumoniae but did not use PCR diagnostics. In another recent study, Gadsby et al [13] achieved pathogen detection in 87% of patients using PCR methods on sputum samples, with S pneumoniae being identified in 36% of cases. Comparison with our work is difficult, however, because Gadsby et al [13] excluded patients unable to produce sputum. These recent studies support the results of the current study, that 20% of CAP is due to S pneumoniae.