Clinical research study
Prospective comparison of three validated prediction rules for prognosis in community-acquired pneumonia

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Abstract

Purpose

We assessed the performance of 3 validated prognostic rules in predicting 30-day mortality in community-acquired pneumonia: the 20 variable Pneumonia Severity Index and the easier to calculate CURB (confusion, urea nitrogen, respiratory rate, blood pressure) and CURB-65 severity scores.

Subjects and methods

We prospectively followed 3181 patients with community-acquired pneumonia from 32 hospital emergency departments (January–December 2001) and assessed mortality 30 days after initial presentation. Patients were stratified into Pneumonia Severity Index risk classes (I–V) and CURB (0–4) and CURB-65 (0–5) risk strata. We compared the discriminatory power (area under the receiver operating characteristic curve) of these rules to predict mortality and their accuracy based on sensitivity, specificity, predictive values, and likelihood ratios.

Results

The Pneumonia Severity Index (risk classes I–III) classified a greater proportion of patients as low risk (68% [2152/3181]) than either a CURB score <1 (51% [1635/3181]) or a CURB-65 score <2 (61% [1952/3181]). Low-risk patients identified based on the Pneumonia Severity Index had a slightly lower mortality (1.4% [31/2152]) than patients classified as low-risk based on the CURB (1.7% [28/1635]) or the CURB-65 (1.7% [33/1952]). The area under the receiver operating characteristic curve was higher for the Pneumonia Severity Index (0.81) than for either the CURB (0.73) or CURB-65 (0.76) scores (P <0.001, for each pairwise comparison). At comparable cut-points, the Pneumonia Severity Index had a higher sensitivity and a somewhat higher negative predictive value for mortality than either CURB score.

Conclusions

The more complex Pneumonia Severity Index has a higher disciminatory power for short-term mortality, defines a greater proportion of patients at low risk, and is slightly more accurate in identifying patients at low risk than either CURB score.

Section snippets

Study sites and patients

This study was conducted between January and December 2001 as part of a clinical trial to assess the effectiveness of 3 practice guideline implementation strategies (low, moderate, and high intensity) for pneumonia in 32 hospital emergency departments in Pennsylvania (n = 16) and Connecticut (n = 16).19 The institutional review boards of all participating study sites approved all study procedures. The study design and characteristics of participating emergency departments were described

Study sample

Of the 4506 identified patients with pneumonia who met eligibility criteria, 3615 (80%) were initially enrolled. Nonenrolled individuals tended to be older (mean age 74 vs. 63 years) and more likely to be resident in nursing homes (36% vs. 4.9%) than enrolled patients. After excluding 434 patients who either failed to meet eligibility criteria based on chart review (n = 293), were missing follow-up information for 30-day mortality (n = 57), lacked documentation of informed consent (n = 33),

Discussion

Our comparison shows that the Pneumonia Severity Index has a higher discriminatory power for predicting 30-day mortality than either CURB severity score. Low-risk patients identified using the Pneumonia Severity Index have a slightly lower mortality and a slightly higher negative predictive value for death than low-risk patients identified using either CURB severity score. Even when the CURB severity scores were converted into more complex, 2-step prediction rules using the Pneumonia Severity

Acknowledgments

The authors would like to acknowledge the important contributions of the individuals listed below for serving the following key roles on the project:

Study Site Investigators. These individuals were responsible for facilitating the initiation and conduct of the trial at the local hospital level:

Connecticut: Michael L. Carius, MD, Thomas Ceddia, MD, Ian Cummings, MD, Robert Femia, MD, Bernard J. Ferguson IV, MD, William Gemmell, MD, Robert J. Grant, MD, Steven T. Holland, MD, Thomas J. Koobatian,

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  • Cited by (0)

    This study was supported by grant RO1 HS10049-03 from the Agency for Healthcare Research and Quality, Rockville, Maryland. Dr. Aujesky was supported in part by the Novartis Research Foundation and Dr. MJ Fine was supported in part by a K24 career development award from the National Institute of Allergy and Infectious Diseases.

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