Severe community-acquired pneumonia in ICUs: prospective validation of a prognostic score

Abstract

Objective: To determine predictors of intensive care unit (ICU) mortality in patients with community-acquired pneumonia (CAP), to develop a pneumonia-specific prognostic index, and to evaluate this index prospectively.

Design: Combined retrospective and prospective clinical study over two periods: January 1987-December 1992 and January 1993-December 1994.

Setting: Four medical ICUs in the north of France.

Patients: Derivation cohort: 335 patients admitted to one ICU were retrospectively studied to determine prognosis factors and to develop a pneumonia-specific prognostic index. Validation cohort: 125 consecutive patients, admitted to four ICUs, were prospectively enrolled to evaluate this index.

Results: In the derivation cohort, 16 predictors of mortality were identified and assigned a value directly proportional to their magnitude in the mortality model: aspiration pneumonia (-0.37), grading of sepsis > or = 11 (-0.2), antimicrobial combination (-0.01), Glasgow score > 12+mechanical ventilation (MV) (+0.09), serum creatinine > or = 15 mg/l (+0.22), chest involvement shown by X-ray > or = 3 lobes (+0.28), shock (+0.29), bacteremia (+0.29), initial MV (+0.29), underlying ultimately or rapidly fatal illness (+0.31), Simplified Acute Physiology Score > or = 12 (+0.49), neutrophil count < or = 3500/ mm3 (+0.52), acute organ system failure score > or = 2 (+0.64), delayed MV (+0.67), immunosuppression (+1.38), and ineffective initial antimicrobial therapy (+1.5). An index was obtained by adding each patient's points. According to a receiver operating characteristic curve, the cut-off value of this index was 2.5. In the validation cohort, an index of > or = 2.5 could predict death with a positive predictive value of 0.92, sensitivity 0.61, and specificity 0.98.

Conclusion: This index, which performs well in classifying patients at high-risk of death, may help physicians in initial patient care (appropriateness of the initial antimicrobial therapy) and guide future clinical research (analysis and design of therapeutic trials).