Pulmonology
PSI / PORT Score (Pneumonia)
30-day mortality risk in community pneumonia.
Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.
Background
The Pneumonia Severity Index (PSI), developed by the Pneumonia Outcomes Research Team (PORT), predicts 30-day mortality in community-acquired pneumonia (CAP) and supports the decision between outpatient and inpatient care. It uses 20 variables spanning demographics (age, sex, nursing-home residence), comorbidities (neoplasia, liver, cardiac, cerebrovascular and renal disease), examination findings (mental status, respiratory rate, blood pressure, temperature, pulse) and laboratory/radiology results (pH, urea, sodium, glucose, haematocrit, oxygenation and pleural effusion). Age in years forms the base score, with points added or subtracted for each factor. Patients are sorted into five risk classes (I–V) of increasing mortality.
Interpreting the result
After identifying any low-risk class I patients on history and examination, the point total assigns the remaining patients to classes II–V: ≤70 points is class I–II (low risk, suitable for outpatient care), 71–90 is class III (low-to-moderate, brief observation or short admission), 91–130 is class IV (moderate-to-high, admit) and >130 is class V (high risk, consider critical care). Mortality rises steeply from well under 1% in classes I–II to roughly a quarter to a third in class V. The score supports but does not replace judgement about oxygenation, comorbidity and social circumstances.
Advice
Class assignment: ≤70 (I–II), 71–90 (III), 91–130 (IV), >130 (V). Use with clinical judgement, oxygenation and social factors.
Worked example
A 75-year-old man with congestive heart failure, a respiratory rate of 32/min and urea of 12 mmol/L scores 75 (age) + 10 (heart failure) + 20 (respiratory rate) + 20 (urea) = 125 points. This places him in class IV (moderate-to-high risk), so hospital admission is recommended.
Pearls / pitfalls
- PSI is more complex than CURB-65 and tends to favour outpatient management by weighting age heavily, so younger patients with severe disease can be under-scored.
- It is a mortality predictor, not an admission rule: hypoxia, inability to take oral treatment or adverse social circumstances can justify admission at a low class.
- Female sex subtracts 10 points, which can mask severity in older women — interpret the class alongside the clinical picture.
- It does not directly identify the need for intensive care; class V should prompt critical-care assessment but ICU decisions use additional criteria.
Evidence & validation
Derived and validated by Fine and colleagues in a cohort of more than 38,000 patients and confirmed prospectively, the PSI is one of the most extensively validated CAP severity tools and is referenced alongside CURB-65 in major pneumonia guidelines including those of the IDSA/ATS and BTS.
Frequently asked questions
How does PSI differ from CURB-65?
PSI uses 20 variables and five risk classes, while CURB-65 uses five. PSI is better validated for identifying low-risk outpatients but is more cumbersome; CURB-65 is quicker at the bedside.
What PSI score allows outpatient treatment?
Classes I and II (roughly ≤70 points) indicate low mortality and generally support outpatient care, provided oxygenation, oral intake and social factors are acceptable.
Why does female sex reduce the score?
The original derivation found lower mortality in women for any given set of findings, so female sex subtracts 10 points. This can under-represent severity in older women, so combine the class with clinical judgement.
Does PSI decide who needs intensive care?
Not directly. Class V flags high mortality and should prompt critical-care assessment, but ICU admission depends on additional physiological and clinical criteria.
Can PSI be used without blood tests?
No — several inputs are laboratory values (pH, urea, sodium, glucose, haematocrit, oxygenation), so PSI requires investigations. Use CRB-65 if bloods are unavailable.
References
- Fine MJ, Auble TE, Yealy DM, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997;336(4):243–250.
- Metlay JP, Waterer GW, Long AC, et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. ATS/IDSA Clinical Practice Guideline. Am J Respir Crit Care Med. 2019.
About the creator
Fine MJ et al.
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