A prognostic rule for elderly patients admitted with community-acquired pneumonia

PURPOSE: We sought to identify admission characteristics predicting mortality in elderly patients hospitalized with community-acquired pneumonia and to develop a prognostic staging system and discriminant rule. PATIENTS AND METHODS:We retrospectively analyzed data from 2,356 patients aged greater than or equal to 65 years admitted with community-acquired pneumonia. Multivariable analyses of a derivation cohort (n = 1,000) identified characteristics associated with hospital mortality. A staging system and discriminant rule based on these characteristics were tested in a validation cohort (n = 1,356). Our discriminant rule was compared with a rule formulated from a heterogeneous adult population with community-acquired pneumonia. RESULTS: Hospital mortality rates were 9% (derivation cohort) and 12% (validation cohort). We identified five independent predictors of mortality: age greater than or equal to 85 years [odds ratio 1.8 (95% confidence interval 1.1-3.1)], comorbid disease [odds ratio 4.1 (2.1-8.1)], impaired motor response [odds ratio 2.3 (1.4-3.7)], vital sign abnormality [odds ratio 3.4 (2.1-5.4)], and creatinine level greater than or equal to 1.5 mg/dL [odds ratio 2.5 (1.5-4.2)]. These variables stratified patients into four distinct stages with increasing mortality in the derivation cohort (Stage 1, 2%; Stage 2, 7%; Stage 3, 22%; Stage 4, 45%; P = 0.001) as well as in the validation cohort (Stage 1, 4%; Stage 2, 11%; Stage 3, 23%; Stage 4, 41%; P = 0.001). The discriminant rule developed from the derivation cohort had greater overall accuracy (77.1%) in the validation cohort than a rule formulated from a heterogeneous adult population (68.0%, P = 0.001). CONCLUSION: Elderly patients with community-acquired pneumonia have characteristics at admission that can predict mortality. Our staging system and discriminant rule improve prognostic stratification of these patients. Am J Med. 1999;106:20-28. (C) 1999 by Excerpta Medica, Inc.