Pneumonia Severity Index Calculator (PSI / PORT Score)
Calculate the Pneumonia Severity Index (PSI / PORT score) for community-acquired pneumonia — age, comorbidities, exam and lab findings — with risk class I–V, 30-day mortality and suggested site of care.
How it works
PSI = age in years (women: age − 10) + nursing home 10 + neoplastic disease 30 + liver disease 20 + heart failure 10 + cerebrovascular disease 10 + kidney disease 10 + altered mental status 20 + RR ≥ 30 20 + SBP < 90 20 + temperature < 35 or ≥ 40 °C 15 + pulse ≥ 125 10 + pH < 7.35 30 + BUN ≥ 30 mg/dL 20 + sodium < 130 20 + glucose ≥ 250 mg/dL 10 + hematocrit < 30% 10 + PaO₂ < 60 mmHg or SpO₂ < 90% 10 + pleural effusion 10. Class I: age ≤ 50 with none of the 5 comorbidities or 5 exam findings; class II ≤ 70; III 71–90; IV 91–130; V > 130.
The Pneumonia Severity Index (Fine et al., New England Journal of Medicine 1997, the PORT study) sorts adults with community-acquired pneumonia into five risk classes for 30-day mortality. Classes I–II can usually be treated as outpatients, class III may need a short observation stay and classes IV–V are usually admitted. The PSI is more accurate than CURB-65 for identifying low-risk patients, but it relies heavily on age and should always be combined with clinical judgement, oxygen needs and social circumstances.
Worked example
A 72-year-old man with heart failure (+10), respiratory rate 32 (+20) and BUN 36 mg/dL (+20) scores PSI = 72 + 10 + 20 + 20 = 122 points: risk class IV, with 9.3% 30-day mortality in the PORT validation cohort — hospital admission is usually advised.
Sources: Fine MJ et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med 1997 · ATS/IDSA guideline for community-acquired pneumonia (2019)
Frequently asked questions
What do the PSI risk classes mean?
Class I (0.1% mortality) and class II (0.6%) are low risk and usually managed as outpatients; class III (0.9%) may need brief observation; class IV (9.3%) and class V (27.0%) are usually admitted, class V often to a higher level of care.
What is the difference between PSI and CURB-65?
CURB-65 uses five simple items and is quick at the bedside. The PSI uses 20 items including lab results; it identifies more patients who are safe to treat at home but is longer to complete.
Why does a woman subtract 10 from her age?
In the PORT derivation cohort women had lower mortality than men of the same age, so the score uses age minus 10 for women. Nursing home residence adds 10 points.
Can a young patient be class I without lab tests?
Yes. Step 1 of the algorithm assigns class I to patients aged 50 or under with none of the five comorbidities and none of the five exam abnormalities; no blood tests are needed for the score.
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Clinical decision tool for education and for use by trained clinicians alongside clinical judgement — not a diagnosis and not a substitute for medical assessment. Scores validated in specific populations may not apply to every patient.