Making sense of scoring systems in community acquired pneumonia

The site of care decision is one of the most important in the management of patients with community-acquired pneumonia (CAP). Several scoring systems have been developed to predict mortality risk in CAP, and these have been applied to guide physicians about whether patients should be admitted to the hospital or to the intensive care unit (ICU). However, these tools were initially developed to predict mortality risk, and studies have demonstrated that the risk for death does not always equate with need for hospitalization or ICU care. The most widely studied scoring systems are the Pneumonia Severity Index (PSI) and the CURB-65 (a modification of the British Thoracic Society rule). Each has advantages and limitations, with the more-complex PSI developed to identify low-mortality risk patients, and the CURB-65, which is simpler, being developed to easily identify more severely ill individuals. No scoring system can replace clinical judgement about the admission decision, and prospective studies have shown that physicians still admit at least 30-60% of low mortality risk patients when using the PSI to guide this decision. Limitations of these prognostic tools include their variable utility in the elderly, and their failure to include certain comorbidities (COPD, immune suppression) and social factors, in their calculations. The need for ICU care is also not well-defined by measuring the PSI or CURB-65, and other tools such as those developed by the Infectious Diseases Society of America/American Thoracic Society (IDSA/ATS) guideline committee and the SMART-COP rule may have greater utility for this purpose. In the future, measurements of serum biomarkers, such as procalcitonin, may augment the information provided by prognostic scoring tools for patients with CAP.