Yeah, it's Pneumonia, But How Bad is it Really?
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According to the American Thoracic Society (ATS) in 2018, 1 million patients required hospitalization for pneumonia and there were 50,000 associated deaths. Pneumonia was the leading cause of sepsis and septic shock and not surprisingly therefore qualified in the top 10 most expensive inpatient hospitalizations.(1) Given these findings, some have sought opportunity to develop mechanisms to assess and safely triage pneumonia patients to either inpatient or outpatient treatment strategies based upon pneumonia severity scores. In October 2019, the Infectious Diseases Society of America (IDSA) in conjunction with the ATS published recommendations for the assessment, treatment and disposition of immunocompetent adult patients with community acquired pneumonia which included several clinical decision rules also known as pneumonia severity scores.(2) The recommended decision rules and several associated, emerging tools are reviewed here.
Hospital or Home?
The IDSA/ATS guidelines favor the use of the Pneumonia Severity Index (PSI)(3) to determine inpatient versus outpatient treatment for community acquired pneumonia. The PSI assigns patients to five risk classes. Age greater than 50 years, select comorbidities or physiologic red flags earn a patient a minimum level II risk. If none of these apply, then the patient is risk class I and can be treated as an outpatient. Points are assigned for the noted comorbidities as well as physiologic parameters to generate a final score, risk class and recommendations for disposition in risk classes II- V. The PSI is favored for its greater sensitivity particularly in the lower risk classifications and therefore its ability to safely triage more patients to outpatient treatment however it requires a considerable number of data inputs some of which may not be readily available in some settings. Conversely the CURB-65 score (4) is supported as an alternative scoring system for its ease of use with a convenient number of inputs which are correlated with a similar risk stratification scheme, however may not perform as consistently as the PSI particularly when applied to lower risk populations.(5)
https://www.mdcalc.com/psi-port-score-pneumonia-severity-index-cap
https://www.mdcalc.com/curb-65-score-pneumonia-severity
Floor or ICU?
For determining level of care, floor versus ICU, in the patient hospitalized with pneumonia the IDSA/ATS recommend the use of their major and minor criteria(6-7). However, there is recognition of the validity of emerging tools such as the SMART COP (8) and there is notable overlap in the parameters utilized in these decision tools. Regarding the major and minor criteria, the guidelines recommend ICU level care to patients with one of the major criteria or three or more of the minor criteria. The SMART COP tool functions like other calculators recommending ICU admission at a score of 5 or greater.
Risk for multi-drug resistance?
There continues to be development of other tools not explicitly covered in the IDSA / ATS guidelines to assist with a variety of patient populations and the IDSA/ATS express support for the continued development of well validated clinical decision tools. One of these is the DRIP score which seeks to assess patient risk for acquisition of multi drug resistant pneumonia.(9) A threshold of 4 points derived from major and minor risk factors determines the need for extended spectrum versus standard antibiotic regimens which might be further determined in the context of local antibiograms and treatment setting.
https://www.mdcalc.com/drug-resistance-pneumonia-drip-score
In summary, the 2019 IDSA/ATS guidelines for the treatment of immunocompetent adults with community acquired pneumonia recommend the use of several pneumonia severity scores in combination with clinician judgement to determine patient disposition to either inpatient or outpatient as well as ICU level treatment settings. These guidelines emphasize the use of the Pneumonia Severity Index as well as the IDSA/ATS major and minor criteria though a variety of other tools have been developed and continue to be validated. Many of these scoring tools are conveniently located on the website MDcalc (10) which further promotes clinical integration.
References
American Thoracic Society. Top 20 Pneumonia Facts - 2018. Available at: www.thoracic.org/patients/patient-resources/resources/top-pneumonia-facts.pdf Accessed 2/5/2020.
Metlay JP, Waterer GW, Long AC et al. Diagnosis and treatment of adults with community acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019; 200(7): e45-e67.
Fine MJ, Auble TE, Yealy DM, Hanusa BH, Weissfeld LA, Singer DE, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med 1997;336:243–250
Lim WS, van der Eerden MM, Laing R, Boersma WG, Karalus N, Town GI, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003;58:377–382
Aujesky D, Auble TE, Yealy DM, Stone RA, Obrosky DS, Meehan TP, et al. Prospective comparison of three validated prediction rules for prognosis in community-acquired pneumonia. Am J Med 2005;118:384–392
Brown SM, Jones BE, Jephson AR, Dean NC; Infectious Disease Society of America/American Thoracic Society 2007. Validation of the Infectious Disease Society of America/American Thoracic Society 2007 guidelines for severe community-acquired pneumonia. Crit Care Med 2009;37:3010–3016.
Marti C, Garin N, Grosgurin O, Poncet A, Combescure C, Carballo S, et al. Prediction of severe community-acquired pneumonia: a systematic review and meta-analysis. Crit Care 2012;16:R141.
Charles PG, Wolfe R, Whitby M, et al. SMART-COP: a tool for predicting the need for intensive respiratory or vasopressor support in community-acquired pneumonia. Clin Infect Dis. 2008;47(3):375-84.
Webb BJ, Dscomb K, Stenehjem E, et al. Derivation and Multicenter Validation of the Drug Resistance in Pneumonia Clinical Prediction Score. Antimicrob Agents Chemother. 2016;60(5):2652-63.
Written by Carl Goff, MD, PGY-1 University of Cincinnati Department of Emergency Medicine
Peer Review, Editing, Posting by Jeffery Hill, MD MEd
