Simplification of the IDSA/ATS criteria for severe CAP using meta-analysis and observational data

The 2007 Infectious Diseases Society of America (IDSA)/American Thoracic Society (ATS) guidelines proposed "minor" criteria to predict intensive care unit (ICU) admission in patients with community-acquired pneumonia. These criteria were based on expert opinion. Consequently, the authors of the guidelines asked investigators to determine whether the score could be simplified by excluding noncontributory variables. Each IDSA/ATS minor criterion was validated using a random effects meta-analysis of seven studies. Variables present in <5% of cases or that were nonsignificantly associated with mortality/ICU admission were excluded. A simplified score excluding these variables was tested for prediction of mortality and ICU admission in an established database. Prediction was assessed using the area under the receiver operator characteristic curve (AUC). Leukopenia (<4000 cells·mm(-3)), thrombocytopenia (<100,000 cells·mm(-3)) and hypothermia <36°C occurred in <5% of cases. A simplified score excluding these variables was performed similarly for prediction of mortality, AUC 0.77 (95% CI 0.73-0.81) versus 0.78 (95% CI 0.74-0.82) (p=0.9) and intensive care unit admission, AUC 0.85 (95% CI 0.82-0.87) versus 0.85 (95% CI 0.82-0.88) (p=0.9). Additional predictors suggested by the IDSA/ATS were associated with mortality and ICU admission, but only incorporating acidosis (pH <7.35) altered the AUC (0.82 (95% CI 0.78-0.86) (p=0.6) for mortality and 0.86 (95% CI 0.82-0.88) (p=0.8) for ICU admission). No improvements were statistically significant. The IDSA/ATS criteria can be simplified by removing three infrequent variables.