• Pneumonia
• respiratory infection

Tools for the assessment of severity of patients with community-acquired pneumonia (CAP) have attracted much interest in the recent past. In this issue of Thorax (see page 878) two systematic reviews and meta-analyses address the value of such tools including no less than 401 and 23 studies.2 Despite different inclusion strategies and statistical approaches, both studies report two main and similar conclusions. First, both the most extensively investigated tools (Pneumonia Severity Index (PSI) and CURB-65/CRB-65) have remarkably favourable power to predict mortality. Secondly, whereas PSI is somewhat better in predicting patients at low risk, the reverse is true for CURB-65/CRB-65. However, these differences are of questionable clinical relevance. Thus, both tools can be regarded as equivalent. CRB-65 is the simplest tool and can easily be remembered and also applied in the outpatient setting. These straightforward conclusions are the result of a decade of intensive and successful work to establish clinically useful tools of severity assessment. So far success is impressive; clinicians now can use a very simple tool as an adjunct to clinical judgement, and studies on patients with CAP can rely on a validated tool for severity stratification.3

At this point, it is worthwhile having a look at the perspectives beyond: where do we have to go from here? Actually, there are many issues that still must be addressed concerning validation in intervention studies and still insufficently recognised ambiguities inherent to the severity scores.

PSI has been prospectively validated in independent populations as a tool to guide site of treatment decisions, and the use of the PSI was associated with a larger proportion of patients in PSI risk classes I and II who were treated in the outpatient environment without compromising their safety.4 No …