How it's calculated
Patients under 50 with none of the listed comorbidities and normal vital signs are automatically Risk Class I. Everyone else is scored: age in years (female age − 10), plus points for nursing home residence, 5 comorbidities, 5 exam findings, and 7 lab/imaging findings, then mapped to Risk Class II–V.
Risk classes
| Class | Points | Approx. 30-day mortality | Site of care |
|---|---|---|---|
| I | Age <50, no risk factors | ~0.1% | Outpatient |
| II | ≤70 | 0.6% | Outpatient |
| III | 71–90 | 0.9–2.8% | Short stay / close follow-up |
| IV | 91–130 | 8.2–9.3% | Inpatient |
| V | >130 | 27–31% | Inpatient, often ICU |
Clinical use
- Used alongside CURB-65 to decide whether a community-acquired pneumonia patient can be safely managed as an outpatient or needs admission.
- PSI/PORT weighs more variables than CURB-65 (including comorbidities and labs), and is generally considered better at identifying genuinely low-risk patients, at the cost of needing more data points to calculate.
- Clinical judgement should override the score where a patient has a clear reason for admission (e.g. inability to take oral medication, unstable social situation) despite a low risk class.
Frequently asked questions
What is the PSI/PORT score used for?
The Pneumonia Severity Index (PSI), also called the PORT Score, predicts 30-day mortality risk in community-acquired pneumonia and helps decide between outpatient treatment, a short observation stay, or inpatient admission.
How is PSI different from CURB-65?
PSI incorporates more variables (age, comorbidities, exam findings, and labs) and is generally more accurate at identifying low-risk patients, while CURB-65 is quicker to calculate at the bedside with just 5 criteria. Many clinicians use CURB-65 for a fast initial impression and PSI for a more detailed risk stratification.
What does Risk Class I mean?
Risk Class I is the lowest-risk group — patients under 50 with no listed comorbidities and normal vital signs — with an approximate 30-day mortality of 0.1%, and no numeric score needs to be calculated.
References
- Fine MJ, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997;336:243-250.
- Mandell LA, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on community-acquired pneumonia in adults. Clin Infect Dis. 2007;44:S27-72.