Pneumonia Severity Index (PSI/PORT) Calculator

The Pneumonia Severity Index, also known as the PORT score, is a validated tool that estimates 30-day mortality in adults with community-acquired pneumonia and sorts them into five risk classes. Its main value is identifying low-risk patients who can be safely managed as outpatients, which reduces unnecessary admissions.

How it works

The score is the sum of weighted points across four groups of variables. Age is the foundation: for men the age in years is added directly, and for women age minus 10 is used. Points are then added for being a nursing home resident, for each comorbidity, for each abnormal physical finding, and for each abnormal lab or imaging result. The published weighting groups the contributors broadly as follows: an age term plus a fixed addition for nursing-home residence; comorbidity points (neoplastic disease carries the heaviest weight, followed by liver disease, with congestive heart failure, cerebrovascular disease and renal disease each weighted lower); examination points for altered mental status, a raised respiratory rate, low systolic blood pressure, an abnormal temperature and a fast pulse; and laboratory or imaging points for arterial acidosis, a raised blood urea nitrogen, low sodium, raised glucose, low haematocrit, hypoxaemia and a pleural effusion.

A separate screen identifies Risk Class I: a patient under 50 with no comorbidity and normal vitals is class I without needing the full tally.

Class bands and interpretation

The total maps to a class and an approximate mortality. Class II is 70 points or fewer, class III is 71 to 90, class IV is 91 to 130, and class V is above 130. Classes I and II generally support outpatient care, class III suggests brief observation, and classes IV and V usually warrant admission with class V prompting consideration of intensive care. Always weigh the result against oxygen needs, the ability to take oral antibiotics, and the patient’s home support before deciding on disposition.

Worked example

Consider a 68-year-old woman with congestive heart failure (CHF) and a respiratory rate of 32 breaths per minute at presentation:

• Age term: 68 − 10 = 58 points
• CHF comorbidity: +10 points
• Elevated respiratory rate (≥30): +20 points
• Running total: 88 points → Risk Class III

Now add a blood urea nitrogen above the threshold on the lab results: +20 points, pushing the total to 108 → Risk Class IV, where admission is strongly indicated. The example shows how a few abnormal findings can shift disposition from observation to a full inpatient admission.

PSI vs CURB-65: which to use?

PSI excels at confidently ruling out a serious outcome in patients who appear low risk but have multiple modest abnormalities. Its 20-variable breadth means a patient who “looks okay” on five items may still accumulate enough points from age and labs to merit admission. CURB-65 is faster and needs no laboratory, making it valuable in resource-limited settings or rapid triage. In practice many ED departments use both: CURB-65 for speed, PSI to confirm discharge safety in borderline cases.

Common pitfalls

Age dominates the score. A healthy 75-year-old woman scores 65 points from age alone, landing near the top of Class II. This is intentional — older patients are genuinely higher risk — but it means PSI is less well suited to guiding care in very elderly patients where the age contribution may outweigh clinical reality. Social circumstances, oxygen saturation, and the patient’s ability to take oral medication must always temper the algorithm’s output.