Mortality Prediction in Community-Acquired Pneumonia: The end of the road for SIRS?

Close up of doctor studying chest X-ray.

By Martina McGrath, MD
December 19, 2017

In 2016, new consensus guidelines were issued for the clinical criteria for sepsis.1 The qSOFA score, incorporating tachypnea, low blood pressure and altered mental status, was proposed as a rapid, bedside assessment, and an alternative to SIRS criteria, to identify patients at high risk of adverse outcomes.

Several different scoring systems exist for patients with community acquired pneumonia, to assess their risk of poor outcomes. However, an ideal scoring system would accurately discriminate between patients at high and low risk of mortality, to effectively guide therapy, but without overtreating those at low risk.

A cohort study, carried out in Spain and recently published in the American Journal of Respiratory and Critical Care Medicine, performed a clinical decision-making analysis of six different severity scores applicable to patients with community-acquired pneumonia.2 The clinical usefulness of each score was assessed, with in-hospital mortality as the primary outcome.

The scores assessed were:

1. Initial Assessment Tools:

  • SIRS
  • qSOFA
  • Confusion Respiratory Rate and Blood Pressure (CRB) score

2. Further Assessment Tools:

  • Modified SOFA (mSOFA)
  • Confusion, Urea, Respiratory Rate, Blood Pressure and Age (CURB-65) score
  • Pneumonia Severity Index (PSI)

This retrospective analysis of patients admitted between 1996 and 2015 comprised data from 6,874 patients.2 Mean age was 66 years, 30% had chronic respiratory disease at the time of admission, 19% were diabetic, and 42% had microbiological confirmation of infection; 11% were discharged from the ED and 13.8% required ICU admission. The overall in-hospital mortality was 6.4%.

Using detailed computational analysis, the authors assessed the predictive value of each score for mortality, as well assessing their clinical usefulness and risk of overtreatment of low-risk patients.  There was a clear association between qSOFA, CRB, mSOFA, CURB-65, and PSI and in-hospital mortality. CRB and CURB-65 had better predictive values than qSOFA for initial stratification of patients in ED.  While mSOFA had strong predictive value for the need for ICU admission, PSI had the best predictive values for mortality.

Higher SIRS poorly predicted mortality and in some analyses, came close to being a ‘treat all’ strategy. When taking into account both true-positive and false-positive classifications, SIRS did not provide any additional benefit to clinical decision making.

In summary, qSOFA and CRB both performed well in identifying high-risk patients in the ED, without the need for intensive investigations. SIRS showed little value, and indeed over-reliance on SIRS carries a risk of overtreatment of lower risk patients. For more comprehensive assessment, such as those requiring ICU admission, mSOFA and PSI were the strongest tools.


  1. Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA 2016;315:801-10.
  2. Ranzani OT, Prina E, Menendez R, et al. New Sepsis Definition (Sepsis-3) and Community-acquired Pneumonia Mortality. A Validation and Clinical Decision-Making Study. Am J Respir Crit Care Med. 2017;196:1287-97.

Headshot of Dr. McGrathDr. Martina McGrath is an Instructor in Medicine at Harvard Medical School, and a member of the Renal Division, Department of Medicine, at Brigham and Women’s Hospital, both in Boston. Dr. McGrath is the Medical Editor for the Trends in Medicine blog.

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