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Pneumonia Severity Index (PSI / PORT Score)

The Pneumonia Severity Index (Fine 1997) assigns community-acquired pneumonia patients to risk classes I–V by age, comorbidity, exam and lab findings. Classes I–II (≤70 points) are generally suitable for outpatient care, class III (71–90) for brief observation, and classes IV (91–130) and V (>130) for admission, with 30-day mortality about 8–9% and 27–31%.

Age (years)
Sex: Male; Female
Nursing home resident (yes/no, +10)
Neoplastic disease (active cancer) (yes/no, +30)
Liver disease (yes/no, +20)
Congestive heart failure (yes/no, +10)
Cerebrovascular disease (yes/no, +10)
Renal disease (yes/no, +10)
Altered mental status (yes/no, +20)
Respiratory rate (/min)
Systolic blood pressure (mmHg or kPa)
Temperature (°C or °F)
Heart rate (/min)
Arterial pH
BUN (or urea in mmol/L) (mg/dL or mmol/L)
Sodium (mmol/L or mEq/L)
Glucose (mg/dL or mmol/L)
Hematocrit (%)
PaO₂ (arterial) (mmHg or kPa)
SpO₂ (%)
Pleural effusion on imaging (yes/no, +10)

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Interpretation

Result	Meaning
Class I	Age ≤50, no comorbidity, normal vitals/mentation: 0.1–0.4%
Class II (≤70)	0.6–0.7%: outpatient
Class III (71–90)	0.9–2.8%: outpatient or brief observation
Class IV (91–130)	8.2–9.3%: inpatient
Class V (>130)	27.0–31.1%: inpatient, consider ICU

Formula

Age (years; women −10) · nursing home +10 · neoplastic +30 · liver +20 · CHF +10 · cerebrovascular +10 · renal +10 · altered mental status +20 · RR ≥30 +20 · SBP <90 +20 · T <35 or ≥40 °C +15 · HR ≥125 +10 · pH <7.35 +30 · BUN ≥30 mg/dL (11 mmol/L) +20 · Na <130 +20 · glucose ≥250 mg/dL (14 mmol/L) +10 · Hct <30% +10 · PaO₂ <60 mmHg or SpO₂ <90% +10 · pleural effusion +10

Clinical pearls

PSI is weighted heavily by age; a young patient with severe hypoxemia can be in a low class. Do not discharge a patient who needs oxygen.
Missing labs are scored as normal (as in the derivation), which can understate risk.
IDSA/ATS 2019 prefers PSI over CURB-65 for the inpatient-vs-outpatient decision, combined with clinical judgment.

Examples

psi 75M chf rr 32 bp 110/70 temp 38.5 hr 100 bun 35 na 135 pneumonia severity index for a 60 year old woman with cancer, confused, sbp 85, ph 7.30, hr 110, rr 24, temp 37.8 port score 40F, rr 18, sbp 125, temp 38.2, hr 92

FAQ

Which PSI classes can be treated as outpatients?

Classes I and II (and selected class III patients) are generally suitable for outpatient treatment; classes IV and V usually need admission.

PSI or CURB-65?

PSI is more detailed and better validated for identifying low-risk patients; CURB-65 is quicker and better at flagging severe illness.

Evidence

Fine MJ et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med 1997;336:243–50.

Pulmonary & Critical Care · Reviewed 2026-10-14 · Methodology