Pneumonia severity index
The pneumonia severity index [PSI] or PORT Score is a clinical prediction rule that medical practitioners can use to calculate the probability of morbidity and mortality among patients with community acquired pneumonia.
Despite sometimes being used to predict the need for hospitalization in people with pneumonia, the PORT score was not developed to do so and should not be used in that way. Mortality prediction is similar to that when using CURB-65.
Development of the PSI
The rule uses demographics (whether someone is older, and is male or female), the coexistence of co-morbid illnesses, findings on physical examination and vital signs, and essential laboratory findings. This study demonstrated that patients could be stratified into five risk categories, Risk Classes I-V, and that these classes could be used to predict 30-day survival.
Data Source for Derivation & Validation
The rule was derived then validated with data from 38,000 patients from the MedisGroup Cohort Study for 1989, comprising 1 year of data from 257 hospitals across the US who used the MedisGroup patient outcome tracking software built and serviced by Mediqual Systems (Cardinal Health). One significant caveat to the data source was that patients who were discharged home or transferred from the MedisGroup hospitals could not be followed at the 30-day mark, and were therefore assumed to be "alive" at that time. Further validation was performed with the Pneumonia Patient Outcomes Research Team [PORT] (1991) cohort study. This categorization method has been replicated by others and is comparable to the CURB-65 in predicting mortality.
Usage & Application of the PSI
The purpose of the PSI is to classify the severity of a patient's pneumonia to determine the amount of resources to be allocated for care. Most commonly, the PSI scoring system has been used to decide whether patients with pneumonia can be treated as outpatients or as (hospitalized) inpatients. A Risk Class I pneumonia patient can be sent home on oral antibiotics. A Risk Class II-III pneumonia patient may be sent home with IV antibiotics or treated and monitored for 24 hours in hospital. Patients with Risk Class IV-V pneumonia patient should be hospitalized for treatment.
The PSI Algorithm
|Step 1: Stratify to Risk Class I vs. Risk Classes II-V|
|Over 50 years of age||Yes/No|
|Altered mental status||Yes/No|
|Respiratory rate >30/minute||Yes/No|
|Systolic blood pressure <90 mm Hg||Yes/No|
|Temperature <35°C or ≥40°C||Yes/No|
|Congestive heart failure||Yes/No|
|If any "Yes", then proceed to Step 2|
|If all "No" then assign to Risk Class I|
|Step 2: Stratify to Risk Class II vs III vs IV vs V|
|If Male||+Age (yr)|
|If Female||+Age (yr) - 10|
|Nursing home resident||+10|
|Congestive heart failure||+10|
|Physical Exam Findings|
|Altered mental status||+20|
|Respiratory rate >30/minute||+20|
|Systolic blood pressure <90 mm Hg||+20|
|Temperature <35°C or ≥40°C||+15|
|Lab and Radiographic Findings|
|Arterial pH <7.35||+30|
|Blood urea nitrogen ≥30 mg/dl (9 mmol/liter)||+20|
|Sodium <130 mmol/liter||+20|
|Glucose ≥250 mg/dl (14 mmol/liter)||+10|
|Partial pressure of arterial O2 <60mmHg||+10|
|∑ <70 = Risk Class II|
|∑ 71-90 = Risk Class III|
|∑ 91-130 = Risk Class IV|
|∑ >130 = Risk Class V|
PSI Derivation and Validation Data
|Medisgroup Study (1989)||PORT Validation Study (1991) Cohort|
|Derivation Cohort||Validation Cohort||Inpatients||Outpatients||All Patients|
|Risk Class||no. of pts||% died||no. of pts||% died||no. of pts||% died||no. of pts||% died||no. of pts||% died|
Note: % Died refers to 30-day mortality.
- Fine, MJ; Auble, TE; Yealy, DM; Hanusa, BH; Weissfeld, LA; Singer, DE; Coley, CM; Marrie, TJ; Kapoor, WN. et al. (Jan 1997). "A prediction rule to identify low-risk patients with community-acquired pneumonia". N Engl J Med 336 (4): 243–250. doi:10.1056/NEJM199701233360402. PMID 8995086.
- Mark Williams; Scott A. Flanders; Winthrop F. Whitcomb (28 September 2007). Comprehensive hospital medicine: an evidence based approach. Elsevier Health Sciences. pp. 273–. ISBN 978-1-4160-0223-9. Retrieved 11 November 2010.
- Chalmers JD; Singanayagam A; Akram AR et al. (October 2010). "Severity assessment tools for predicting mortality in hospitalised patients with community-acquired pneumonia. Systematic review and meta-analysis". Thorax 65 (10): 878–83. doi:10.1136/thx.2009.133280. PMID 20729231.
- Aujesky D; Auble TE; Yealy DM et al. (2005). "Prospective comparison of three validated prediction rules for prognosis in community-acquired pneumonia". Am. J. Med. 118 (4): 384–92. doi:10.1016/j.amjmed.2005.01.006. PMID 15808136.
- Pneumonia: New Prediction Model Proves Promising
- Pneumonia Severity Index Calculator
- Community-Acquired Pneumonia Mortality Risk for Adults (Pneumonia Patient Outcomes Research Team - PORT) Score Calculator
- Figure 1, Halm E, Teirstein A. Management of Community-Acquired Pneumonia. NEJM 2002 347 (25): 2039