Microbial aetiology, outcomes, and costs of hospitalisation for community-acquired pneumonia

Introduction: Community-acquired pneumonia (CAP) carries a high burden worldwide, in particular in the elderly. Of all CAP episodes in elderly 20-40% are treated in-hospital. This results in considerable health care costs. Knowledge on exact costs of CAP is indispensable to estimate cost-effectiveness of new strategies aiming to prevent and/or improve clinical outcome of CAP. Aim: To investigate clinical outcome and especially costs of hospitalisation in CAP in relation to microbial aetiology. Methods: An observational analysis in a cohort of 505 patients hospitalised with confirmed CAP between 2004 and 2010 was performed. Results: Streptococcus pneumoniae was the most identified causative pathogen (25%), followed by Coxiella burnetii (6%) and Haemophilus influenzae (5%). Overall median length of hospital stay was 8.5 days, in-hospital mortality rate was 4.8%. Total median hospital costs per patient were €3,899 (IQR 2,911-5,684). General ward nursing costs represented the largest share (57%), followed by nursing on the intensive care unit (16%) and diagnostic microbiological tests (9%). In multivariate regression analysis, Pneumonia Severity Index class IV-V, Staphylococcus aureus , and Streptococcus pneumonia as causative pathogen, were independent cost driving factors. Coxiella burnetii was a cost-limiting factor. Conclusion: Costs of hospitalisation for CAP are mainly caused by nursing costs, and increased disease severity and S. pneumoniae and Staphylococcus aureus as causative pathogens are independent cost driving factors. This suggests to focus further research on low-cost interventions aimed at reducing length of hospital stay and prevention of CAP caused by these pathogens.