Impact of guideline-consistent therapy on outcome of patients with healthcare-associated and community-acquired pneumonia

Background: A new category of healthcare-associated pneumonia (HCAP) has been added in the most recent American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) guidelines, since multidrug-resistant (MDR) pathogens are more common in patients with HCAP than in those with community-acquired pneumonia (CAP). The optimal empirical management of patients with HCAP remains controversial and adherence to guidelines is inconsistent. Methods: A retrospective cohort study of 3295 adults admitted for pneumonia in an academic centre of Canada, between 1997 and 2008. Results: MDR pathogens were more common among patients with HCAP than in those with CAP, but less so than in other studies. Compared with patients with CAP, those with HCAP had a higher all-cause 30 day mortality [68/563 (12%) versus 201/2732 (7%); P<0.001] and more frequent need for mechanical ventilation [78/563 (14%) versus 276/2732 (10%); P=0.01]. In patients with CAP, mortality was lower when treatment was concordant with guidelines [86/1557 (6%) versus 109/1097 (10%) if discordant; adjusted odds ratio 0.6 (0.4-0.8); P<0.001]. In HCAP, mortality was similar whether or not empirical treatment was concordant with guidelines [6/35 (17%) versus 18/148 (12%) if discordant; P=0.4]. However, 30 day mortality tended to be higher when the empirical treatment was microbiologically ineffective [4/22 (18%) versus 17/187 (9%) when effective; P=0.3]. Conclusions: HCAP is associated with worse outcomes than CAP. MDR pathogens were implicated in only a small fraction of HCAP cases. In our study, unlike CAP, non-respect of current HCAP guidelines had no adverse effect on the ultimate outcome. Strategies for the empirical management of HCAP should be tailored to the local epidemiological context.