Validation of predictive rules and indices of severity for community acquired pneumonia

Background: A study was undertaken to validate the modified American Thoracic Society (ATS) rule and two British Thoracic Society (BTS) rules for the prediction of ICU admission and mortality of community acquired pneumonia and to provide a validation of these predictions on the basis of the pneumonia severity index ( PSI). Method: Six hundred and ninety six consecutive patients ( 457 men (66%), mean (SD) age 67.8 (17.1) years, range 18 - 101) admitted to a tertiary care hospital were studied prospectively. Of these, 116 (16.7%) were admitted to the ICU. Results: The modified ATS rule achieved a sensitivity of 69% (95% CI 50.7 to 77.2), specificity of 97% ( 95% CI 96.4 to 98.9), positive predictive value of 87% ( 95% CI 78.3 to 93.1), and negative predictive value of 94% ( 95% CI 91.8 to 95.8) in predicting admission to the ICU. The corresponding predictive indices for mortality were 94% ( 95% CI 82.5 to 98.7), 93% ( 95% CI 90.6 to 94.7), 49% ( 95% CI 38.2 to 59.7), and 99.5% ( 95% CI 98.5 to 99.9), respectively. These figures compared favourably with both the BTS rules. The BTS-CURB criteria achieved predictions of pneumonia severity and mortality comparable to the PSI. Conclusions: This study confirms the power of the modified ATS rule to predict severe pneumonia in individual patients. It may be incorporated into current guidelines for the assessment of pneumonia severity. The CURB criteria may be used as an alternative tool to PSI for the detection of low risk patients.