Original Contribution
Validation of the Infectious Diseases Society of America/American Thoracic Society criteria to predict severe community-acquired pneumonia caused by Streptococcus pneumoniae,☆☆

https://doi.org/10.1016/j.ajem.2008.07.037Get rights and content

Abstract

Background

Severe community-acquired pneumonia (CAP) is usually defined as pneumonia that requires intensive care unit (ICU) admission; the primary pathogen responsible for ICU admission is Streptococcus pneumoniae. In this study, the 2007 Infectious Diseases Society of America/American Thoracic Society (IDSA/ATS) consensus criteria for ICU admission were compared with other severity scores in predicting ICU admission and mortality.

Methods

We retrospectively studied 158 patients with pneumococcal CAP (1999-2003). Clinical and laboratory features at the emergency department were recorded and used to calculate the 2007 IDSA/ATS rule, the 2001 ATS rule, 2 modified 2007 IDSA/ATS rules, the Pneumonia Severity Index (PSI), and the CURB (confusion, urea, respiratory rate, blood pressure) score. The sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were assessed for the various indices. We also determined the criteria that were independently predictive of ICU admission and of mortality in our population.

Results

The 2007 IDSA/ATS criteria performed as well as the 2001 ATS rule in predicting ICU admission both demonstrated high sensitivity (90%) and NPV (97%). For the prediction of mortality, the best tool proved to be the PSI score (sensitivity, 95%; NPV, 99%). The variables associated with ICU admission in this patient population included tachypnea, confusion, Pao2/Fio2 ratio of 250 or lower, and hypotension requiring fluid resuscitation. Mechanical ventilation and PSI class V were independently associated with mortality.

Conclusions

This study confirms the usefulness of the new criteria in predicting severe CAP. The 2001 ATS criteria seem an attractive alternative because they are simple and as effective as the 2007 IDSA/ATS criteria.

Introduction

Despite advances in antimicrobials and vaccines, community-acquired pneumonia (CAP) remains a common illness and a major cause of morbidity and mortality. Approximately 5 to 6 million people are diagnosed with CAP annually, whereas more than 1 million require hospitalization [1], [2]. The average mortality for hospitalized patients is 13.7% but ranges from approximately 8% in patients not requiring admission to an intensive care unit (ICU) to 36.5% for patients admitted to the ICU [3], [4], [5]. The pathogen responsible for CAP is difficult to identify in many cases; however, Streptococcus pneumoniae remains the most commonly isolated pathogen. In a large meta-analysis, it was found to be responsible for two thirds of bacteremic pneumonia cases and one third of patients admitted to the ICU [3].

Community-acquired pneumonia is a disease with a wide spectrum of presentation, ranging from a mild self-limiting condition to one that is occasionally fatal. Although there is no universally accepted definition for severe CAP, it is usually referred to as one that requires ICU admission. Approximately 10% of patients who are hospitalized with CAP require ICU admission [6]. In most situations, the decision to admit a patient to the ICU depends on the clinical judgment of the physician and on that of local practices in the health care system. Because delayed transfer to the ICU has been shown to be associated with increased mortality, there is a need for establishment of valid criteria for the identification of severe CAP and subsequent ICU admission. Various prognostic models such as the 2001 ATS guidelines [7], the criteria of the British Thoracic Society [8], and the Pneumonia Severity Index (PSI) score [9] have been used to evaluate the severity of CAP and to predict mortality rates for different patients. In general, these rules are thought to be overly sensitive and poorly specific. As a result, the 2007 Infectious Diseases Society of America/American Thoracic Society (IDSA/ATS) consensus recommend new criteria for ICU admission [6]. The new proposed criteria for severe CAP have not been validated in any clinical population. The aim of this study was to evaluate these criteria and compare their accuracy with other severity scores for prediction of ICU admission and mortality in a population with CAP caused by S pneumoniae.

Section snippets

Study design

This was a retrospective cohort study of adult patients admitted to Hartford Hospital between 1999 and 2003 with documented pneumococcal CAP, who were previously included in a pharmacoeconomic analysis [10]. Hartford Hospital is an 810-bed private teaching hospital located in Hartford, Conn. This study was reviewed and approved by our hospital's institution review board; no consent was required because the data were already in existence.

Patients

We studied all patients with CAP admitted to the hospital

Population

A total of 158 patients met the criteria and were included in the analysis (Table 1). Thirty-one (19.6%) patients were admitted to the ICU directly from the ED, and 11 (7%) were transferred to the ICU from the floors later during their hospitalization (3 on the first day, 5 by day 3, and 3 afterward). The overall mortality rate was 12.7%, 7.9% for patients not initially admitted to the ICU and 32.3% for those admitted to the ICU. Mortality was 45.5% for the 11 patients who were later

Discussion

This is the first study to evaluate the 2007 IDSA/ATS criteria for severe pneumonia and to compare their performance with other published scores for different outcomes, such as ICU admission and mortality in a population with pneumonia caused by S pneumoniae. We observed that the 2007 IDSA/ATS rule was a sensitive tool for ICU admission, but it did not demonstrate superiority to the previous 2001 ATS guidelines. The new guidelines propose a greater number of variables that can be considered to

References (21)

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The study was internally funded by the Center for Anti-Infective Research and Development, Hartford Hospital.

☆☆

Drs. Kuti and Nicolau are employees of the Center for Anti-Infective Research and Development, Hartford Hospital. The authors report no other conflicts of interest.

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