Maybe guidelines are our fate. With the widespread acknowledgement of the principles of evidence-based medicine as the major basis for medical research, the number of evidence-based guidelines following a predefined methodological approach is steadily increasing. Community-acquired pneumonia (CAP) was one of the first diseases to be covered by guidelines. Since then, in addition to the most authoritative American Thoracic Society (ATS)/Infectious Diseases Society of America (IDSA) 1, European Respiratory Society (ERS) 2 and British Thoracic Society (BTS) 3 guidelines, multiple national guidelines have been released and repeatedly updated. Without doubt, the ongoing discussion among international experts covering diverse specialties has substantially stimulated clinical research. Searching the world literature of the last 50 yrs, reviewing and rating every meaningful paper, and putting together the available evidence revealed that there are far more questions than answers regarding even the simplest clinical objectives. Some of these were successfully worked on, with the most impressive result being the derivation and validation of tools for severity assessment as the basis for decisions on treatment settings 4. But, do guidelines on CAP actually improve routine clinical practice?
Several studies have tried to approach this issue. The populations studied were very different: some included all hospitalised patients 5–12, whereas others included subgroups such as outpatients 13 and intensive care unit (ICU) patients 14. Most studies were retrospective in design 5–9, 14 and one relied on a pre–post intervention design 10. The selected outcomes usually covered length of hospital stay and mortality 5–11, 14. Most studies focused on antimicrobial treatment as an intervention variable 6, 8, 9, 11, 14, while others evaluated clinical pathways 5. This heterogeneity of study design means conflicting results are not surprising, although most studies …