Pneumonia Severity Index (PSI/PORT) Calculator

About the Pneumonia Severity Index (PSI/PORT) Calculator

The Pneumonia Severity Index (PSI), also known as the PORT score, is a validated clinical prediction tool that stratifies patients with community-acquired pneumonia (CAP) into five risk classes based on 30-day mortality. Developed by Fine et al. in 1997 and validated in over 50,000 patients, it remains one of the most widely used tools for site-of-care review in CAP.

The PSI assigns points based on demographics (age, sex), comorbidities (cancer, liver disease, heart failure, cerebrovascular disease, renal disease), physical examination findings (altered mental status, tachypnea, hypotension, temperature extremes, tachycardia), and laboratory/imaging results (pH, BUN, sodium, glucose, hematocrit, PaO2, pleural effusion).

Patients in Risk Classes I and II usually fall into low-risk bands. Class III often lands in an observation-style middle zone, while Classes IV and V represent substantially higher-risk groups. The score is best used to frame care-setting review alongside oxygenation, social factors, oral intake, and the rest of the pneumonia assessment.

When This Page Helps

The PSI/PORT score is useful because it turns a long CAP severity checklist into one validated mortality-risk class. That makes it easier to discuss whether a case looks outpatient-leaning, observation-level, or inpatient-leaning before the final care-setting decision is made.

This calculator is most helpful as a structured summary of risk, not as a substitute for oxygenation review, social factors, oral tolerance, or the rest of the pneumonia workup.

How to Use the Inputs

1. Enter patient demographics — age, sex, and nursing home residence status.
2. Select present comorbidities — neoplastic disease, liver disease, CHF, cerebrovascular disease, and renal disease.
3. Enter physical examination findings — mental status, respiratory rate, systolic BP, temperature, and pulse.
4. Enter laboratory values — arterial pH, BUN, sodium, glucose, hematocrit, PaO₂, and pleural effusion status.
5. Review the total PSI score, risk class, predicted 30-day mortality, and care-setting context.
6. Compare with the scoring breakdown to understand which variables contribute most to the score.

Example Calculation

Tips & Best Practices

• Class I requires NO scoring — it is determined by demographics and physical exam alone (age ≤ 50, no comorbidities, normal vitals).
• Always obtain arterial pH, BUN, sodium, glucose, hematocrit, and PaO₂ before calculating the full score.
• Consider CURB-65 as a complementary tool — if either score suggests high risk, lean toward admission.
• Document the PSI score and class alongside the other factors that shape the care-setting decision.
• For immunocompromised patients, PSI may underestimate severity — use lower thresholds for admission.

How PSI Is Best Used

The PSI works best as a structured mortality-risk summary for community-acquired pneumonia. It is especially strong at identifying lower-risk patients, but it should sit beside oxygenation, oral intake, social support, and the broader bedside assessment.

Why Age Matters So Much

Age is heavily weighted in PSI, which improves mortality prediction but can make some younger patients with significant acute illness look lower risk than expected. That is why many clinicians compare PSI with simpler severity tools and with their bedside impression.

Limits of the Score

The PSI does not capture every factor that shapes care-setting review. Immunosuppression severity, multilobar disease burden, inability to take oral therapy, and local follow-up reliability still matter even when the PSI class looks reassuring.

Frequently Asked Questions

• What is the difference between PSI and CURB-65?

  PSI is more comprehensive (20 variables) and better at identifying low-risk patients for outpatient treatment. CURB-65 is simpler (5 variables) and better at identifying high-risk patients. Both are guideline-recommended. PSI may underestimate risk in young patients with severe disease but no comorbidities.

• Can PSI be used for hospital-acquired pneumonia?

  No. The PSI was developed and validated specifically for community-acquired pneumonia. Hospital-acquired and ventilator-associated pneumonia have different risk factors and require different severity assessment tools.

• Does a low PSI score guarantee outpatient safety?

  No. PSI should supplement, not replace, clinical judgment. Social factors (homelessness, inability to take oral medications), hypoxia not captured by PaO2, and clinical instability may warrant admission regardless of PSI class.

• Why does age have such a large impact on the score?

  Age is the baseline for the PSI score because pneumonia mortality increases substantially with age. However, this means young patients with severe disease may be classified as low-risk. Always consider the full clinical picture.

• When should I recalculate the PSI?

  PSI is typically calculated at initial presentation to frame site-of-care review. It is not designed for serial reassessment during hospitalization. For inpatient progress, use clinical stability criteria and the evolving bedside picture instead.

• What does the PSI not account for?

  PSI does not capture social determinants of health, ability to take oral medications, oxygenation on room air vs. supplemental O2, multilobar infiltrates, immunosuppression severity, or the causative pathogen. These factors should be considered separately.