This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
Deciding where to treat pneumonia
Community-acquired pneumonia ranges from a mild infection treated with a few days of antibiotics at home to a life-threatening illness that needs intensive care. Admitting every patient fills hospitals and exposes people to hospital infections; sending the wrong patient home can be fatal. The Pneumonia Severity Index (PSI), developed by Michael Fine and the Pneumonia PORT team and published in 1997, was built to identify patients at low risk of death who can safely be treated as outpatients.
How the score is built
The calculation has two steps.
- Class I check. A patient aged 50 or younger with none of the five comorbidities, a normal mental state and normal vital signs is placed in class I without further testing.
- Points. Everyone else gets points:
- age in years, minus 10 for women, plus 10 for nursing home residents;
- cancer +30, liver disease +20, heart failure +10, cerebrovascular disease +10, kidney disease +10;
- altered mental status +20, respiratory rate of 30 or more +20, systolic pressure below 90 mmHg +20, temperature below 35 °C (95 °F) or 40 °C (104 °F) and above +15, pulse of 125 or more +10;
- arterial pH below 7.35 +30, BUN of 30 mg/dL or more +20, sodium below 130 +20, glucose of 250 mg/dL or more +10, hematocrit below 30% +10, PaO₂ below 60 mmHg or saturation below 90% +10, pleural effusion +10.
Risk classes
| Class | Points | 30-day mortality (derivation) | Usual site of care |
|---|---|---|---|
| I | no points needed | about 0.1% | outpatient |
| II | 70 or less | about 0.6% | outpatient |
| III | 71 to 90 | about 0.9% | outpatient or short stay |
| IV | 91 to 130 | about 9.3% | hospital |
| V | above 130 | about 27% | hospital, consider ICU |
Example
The default example is a 68-year-old man with no comorbidity and moderately abnormal vital signs. Age alone gives him 68 points: class II, a group in which outpatient treatment is usually possible if he can take oral antibiotics and has support at home.
Limits
Age dominates the score, so it can underestimate severity in a young patient with very abnormal vital signs and overestimate it in a healthy older adult. It does not cover immunosuppression, pregnancy, hospital-acquired pneumonia or social factors. The 2019 ATS/IDSA guideline recommends it, together with clinical judgment, and uses separate criteria to decide on intensive care.