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.[1]
Despite sometimes being used to predict the need for hospitalization in people with pneumonia,[2] the PORT score was not developed to do so and should not be used in that way.[citation needed] Mortality prediction is similar to that when using CURB-65.[3]
Contents
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[4] and is comparable to the CURB-65 in predicting mortality.[4]
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 or Risk Class II pneumonia patient can be sent home on oral antibiotics.[5]
- A Risk Class III patient, after evaluation of other factors including home environment and follow-up, may either:[6]
-
- be sent home with oral antibiotics[5]
- be admitted for a short hospital stay with antibiotics and monitoring.[5]
- Patients with Risk Class IV-V pneumonia patient should be hospitalized for treatment.[5]
The PSI Algorithm
The PSI Algorithm is detailed below. An online, automated PSI calculator is available on the US AHRQ website.
| Step 1: Stratify to Risk Class I vs. Risk Classes II-V | |||
| Presence of: | |||
| Over 50 years of age | Yes/No | ||
| Altered mental status | Yes/No | ||
| Pulse ≥125/minute | Yes/No | ||
| Respiratory rate >30/minute | Yes/No | ||
| Systolic blood pressure <90 mm Hg | Yes/No | ||
| Temperature <35°C or ≥40°C | Yes/No | ||
| History of: | |||
| Neoplastic disease | Yes/No | ||
| Congestive heart failure | Yes/No | ||
| Cerebrovascular disease | Yes/No | ||
| Renal disease | Yes/No | ||
| Liver disease | 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 | |||
| Demographics | Points Assigned | ||
| If Male | +Age (yr) | ||
| If Female | +Age (yr) - 10 | ||
| Nursing home resident | +10 | ||
| Comorbidity | |||
| Neoplastic disease | +30 | ||
| Liver disease | +20 | ||
| Congestive heart failure | +10 | ||
| Cerebrovascular disease | +10 | ||
| Renal disease | +10 | ||
| Physical Exam Findings | |||
| Altered mental status | +20 | ||
| Pulse ≥125/minute | +10 | ||
| 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 | ||
| Hematocrit <30% | +10 | ||
| Partial pressure of arterial O2 <60mmHg | +10 | ||
| Pleural effusion | +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 |
| I | 1,372 | 0.4 | 3,034 | 0.1 | 185 | 0.5 | 587 | 0.0 | 772 | 0.1 |
| II (<70) | 2,412 | 0.7 | 5,778 | 0.6 | 233 | 0.9 | 244 | 0.4 | 477 | 0.6 |
| III (71–90) | 2,632 | 2.8 | 6,790 | 2.8 | 254 | 1.2 | 72 | 0.0 | 326 | 0.9 |
| IV (91–130) | 4,697 | 8.5 | 13,104 | 8.2 | 446 | 9.0 | 40 | 12.5 | 486 | 9.3 |
| V (>130) | 3,086 | 31.1 | 9,333 | 29.2 | 225 | 27.1 | 1 | 0.0 | 226 | 27.0 |
| Total | 14,199 | 10.2 | 38,039 | 10.6 | 1343 | 8.0 | 944 | 0.6 | 2287 | 5.2 |
Note: % Died refers to 30-day mortality.
References
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- 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
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