Towards a sensible comprehension of severe community-acquired pneumonia

Four different rules have been suggested and validated for intensive care unit (ICU) admission for community-acquired pneumonia: modified American Thoracic Society (ATS) rule, Infectious Diseases Society of America (IDSA)/ATS rule, España rule, and SMART-COP. Their performance varies, with sensitivity of around 70% and specificity of around 80-90%. Only negative predictive values are consistently high. Critical methodological issues include the appropriate reference for derivation, the populations studied, the variables included, and the time course of pneumonia. Severe community-acquired pneumonia (SCAP) may evolve because of acute respiratory failure or/and severe sepsis/septic shock. Pneumonia-related complications and decompensated comorbidities may be additional or independent reasons for a severe course. All variables included in predictive rules relate to the two principal reasons for SCAP. However, taken as major criteria, they are of little value for clinical assessment. Instead, a limited set of minor criteria reflecting severity seems appropriate. However, predictive rules may not meet principal needs of severity assessment because of failure in sensitivity, ignorance of the potential contribution of complications or decompensated comorbidity to pneumonia severity, and poor sensitivity for the lower extreme in the spectrum of severe pneumonia, i.e., patients at risk of SCAP. We therefore advocate an approach that refers to the evaluation of the need for intensified treatment rather than ICU, based on a set of minor criteria and sensitive to the dynamic nature of pneumonia. Intensified treatment such as monitoring and treatment of acute respiratory failure or/and severe sepsis/septic shock is thought to improve management and possibly outcomes by setting the focus on both patients with severity criteria at admission and those at risk for SCAP.