Repeated pneumonia severity index measurement after admission increases its predictive value for mortality in severe community-acquired pneumonia

Background/Purpose: Severe community-acquired pneumonia (CAP) is associated with high hospital mortality, and accurate assessment of patients is important for supporting clinical decision making. The Pneumonia Severity Index (PSI) is a good tool for predicting disease severity, especially in the low-risk group of patients with CAP. We investigated whether the change in PSI measurement after admission could identify patients at high risk of mortality from CAP. Methods: We prospectively studied 250 inpatients with CAP. PSI was measured at admission and 72 hours later at a tertiary referral medical center from May 2005 to February 2006. The initial and repeated PSI results were compared. Hospital mortality was used as the outcome measure. Results: Initial PSI in high-risk patients (PSI class > IV) had a low specificity (37%), and a low positive predictive value (PPV) (17%). Increased repeated PSI score, as compared with initial score, was associated with an increased mortality rate (from 7.8% to 33.3% in class IV, and 25.3% to 53.3% in class V; p < 0.0001), and improved the predictive value, with 94% specificity and a PPV of 46% for mortality in high-risk patients. Conclusion: Increased PSI score, 72 hours after admission, for patients with CAP improved the predictive value of PSI score and more accurately identified patients with a high risk of mortality.