According to a widespread consensus reflected in all authoritative guidelines, assessment of severity is the key step in the management of patients with community acquired pneumonia (CAP). It is a major criterion in the decision where to treat a patient and it widely determines the amount of diagnostic workup as well as the selection of initial empiric antimicrobial treatment. Overall, it has major implications in terms of outcomes and costs. Two lines of investigation have resulted in two competing tools of severity assessment: the pneumonia severity index (PSI)1 and the CURB score and its modifications (CURB-65, CRB-65).2^–5 In the meantime, it has become evident that the PSI and the CRB-65 score, as the most simple modification of the original CURB score, perform equivalent in terms of prediction of inhospital death. Both predict death in a class 3 pattern, with mortality rates of approximately 1–3% (PSI class I–III, CRB-65 class 1), 8–10% (PSI class IV and CRB-class 2) and 20–30% (PSI class V and CRB-65 class 3).5 6 Both scores also work reasonably well in ambulatory patients.5 However, as the CRB-65 score is far easier to remember and to compute, being based exclusively on variables which can be immediately determined without any technical expense other than blood pressure measurement, this score is the one which will gain general acceptance.7

It is intriguing that such a simple rule is able to predict the risk of death so accurately. Nevertheless, in this issue of Thorax, Chalmers and colleagues8 provide convincing data from a large population showing that the CRB-65 score can be simplified …