Pneumonia Severity Index (PSI/PORT) Calculator
Pneumonia Severity Index (PSI/PORT) Calculator
Score all twenty PSI variables, including the step-1 rule that decides risk class I, and see the 30-day mortality Fine et al published for the class.
Pneumonia Severity Index
20 variables → risk class I–V72-year-old woman, community-acquired pneumonia, congestive heart failure, respiratory rate 32, blood urea nitrogen 34 mg/dL, everything else negative
Two steps, not one
- Step 1
- class I if NOT over 50 and none of: neoplastic, liver, cardiac, cerebrovascular or renal disease; altered mental status; pulse ≥125; respiratory rate ≥30; systolic BP <90; temperature <35 or ≥40
- Step 2
- age in years (minus 10 if female) plus the point values of every item present
- Class II
- 70 points or fewer
- Class III
- 71 to 90 points
- Class IV
- 91 to 130 points
- Class V
- more than 130 points
Worked example
72-year-old woman, community-acquired pneumonia, congestive heart failure, respiratory rate 32, blood urea nitrogen 34 mg/dL, everything else negative
Age 72, female → 72 − 10 = 62 points from age and sex
Congestive heart failure +10; respiratory rate ≥30 +20; BUN ≥30 mg/dL +20
62 + 10 + 20 + 20 = 112 points
Age is over 50, so step 1 excludes class I; 112 is in 91–130 → risk class IV
Class IV 30-day mortality in the MedisGroups validation cohort was 8.2%
Note that 62 of the 112 points — more than half — come from age and sex alone
The twenty PSI variables
| Group | Variable | Points |
|---|---|---|
| Demographic | Age, male | age in years |
| Demographic | Age, female | age in years − 10 |
| Demographic | Nursing home resident | +10 |
| Coexisting illness | Neoplastic disease | +30 |
| Coexisting illness | Liver disease | +20 |
| Coexisting illness | Congestive heart failure | +10 |
| Coexisting illness | Cerebrovascular disease | +10 |
| Coexisting illness | Renal disease | +10 |
| Examination | Altered mental status | +20 |
| Examination | Respiratory rate ≥30/min | +20 |
| Examination | Systolic BP <90 mmHg | +20 |
| Examination | Temperature <35 °C or ≥40 °C | +15 |
| Examination | Pulse ≥125/min | +10 |
| Laboratory / radiograph | Arterial pH <7.35 | +30 |
| Laboratory / radiograph | Blood urea nitrogen ≥30 mg/dL | +20 |
| Laboratory / radiograph | Sodium <130 mmol/L | +20 |
| Laboratory / radiograph | Glucose ≥250 mg/dL | +10 |
| Laboratory / radiograph | Haematocrit <30% | +10 |
| Laboratory / radiograph | PaO₂ <60 mmHg | +10 |
| Laboratory / radiograph | Pleural effusion | +10 |
30-day mortality by risk class, in all three of Fine's cohorts
| Class | Points | Derivation cohort | MedisGroups validation (n = 38,039) | PORT validation (n = 2,287) |
|---|---|---|---|---|
| I | step 1, no total | 0.4% | 0.1% (n = 3,034) | 0.1% (n = 772) |
| II | ≤ 70 | 0.7% | 0.6% (n = 5,778) | 0.6% (n = 477) |
| III | 71 – 90 | 2.8% | 2.8% (n = 6,790) | 0.9% (n = 326) |
| IV | 91 – 130 | 8.5% | 8.2% (n = 13,104) | 9.3% (n = 486) |
| V | > 130 | 31.1% | 29.2% (n = 9,333) | 27.0% (n = 226) |
PSI against CURB-65
| PSI / PORT | CURB-65 | |
|---|---|---|
| Variables | 20 | 5 |
| Best at | Identifying low-risk patients who can be treated as outpatients | Being quick, memorable and calculable at the bedside |
| Dominated by | Age, which can supply most of the total on its own | Nothing — all five items carry one point |
| Needs | Arterial gas, a chest radiograph, sodium, glucose, haematocrit, urea | Confusion, urea, respiratory rate, blood pressure, age |
| Weakness | Under-weights severe physiological derangement in a young patient | Under-weights comorbidity and social circumstances |
| On this site | This page | CURB-65 score calculator |
Why a young patient with a pH of 7.2 can still come out as class I
The Pneumonia Severity Index — the PORT score — runs in two steps, and the first step is the one that gets dropped. Step 1 assigns risk class I to a patient who is not over 50 and has none of five comorbidities (neoplastic, liver, cardiac, cerebrovascular or renal disease) and none of five examination findings (altered mental status, pulse ≥125, respiratory rate ≥30, systolic pressure below 90 mmHg, temperature below 35 °C or 40 °C and above). Only if one of those eleven is present does the twenty-item point total get calculated at all, and the total then sorts the patient into classes II to V at 70, 90 and 130 points. This calculator implements both steps, which is why a patient can be shown a point total and a class I verdict at the same time.
That structure is also the score's most-cited weakness. The eleven step-1 findings do not include a single laboratory or radiographic result, so a 40-year-old with an arterial pH of 7.25, a PaO₂ of 52 mmHg, a sodium of 126 and a pleural effusion — a patient most clinicians would admit to a high-dependency bed — satisfies step 1 and is assigned to class I, the group the score exists to send home. The PSI under-weights age-independent physiological derangement because age and its proxies dominate the arithmetic: a 78-year-old man scores 78 points, class III, before anything at all has been found wrong with him, while the whole of the laboratory and radiographic panel can only add 110. The calculator prints the points coming from age and sex separately for exactly this reason — it is usually the largest single contribution.
Against CURB-65, the division of labour is clear. The PSI is the better instrument for identifying patients at low risk who can safely be treated as outpatients, which is what it was derived to do — Fine's paper is titled "A prediction rule to identify low-risk patients". CURB-65 is simpler, far better known and needs only five items, none of them a blood gas or a radiograph, which is why it is the one that actually gets used on a ward round. Neither score decides whether to give antibiotics, and neither knows whether the patient can get home, take tablets or be reviewed tomorrow.
Two practical points about the inputs. The original states blood urea nitrogen in mg/dL, not urea in mmol/L; 30 mg/dL of BUN is about 10.7 mmol/L of urea, and the urea/BUN converter will do the conversion if your report is in SI units. And the oxygenation item is a PaO₂ below 60 mmHg (8.0 kPa). Many implementations accept an oxygen saturation below 90% instead, which is convenient and widely done, but it does not appear in the point table as reproduced from the original, so this calculator scores the PaO₂ and says so rather than quietly substituting. This supports a clinician's judgement rather than replacing it. It is arithmetic on the figures entered, and it knows nothing about the patient in front of you.
Frequently asked questions
How is PSI risk class I decided?
By absences, not by points. A patient is class I if they are not over 50 years old and have none of neoplastic, liver, cardiac, cerebrovascular or renal disease, and none of altered mental status, pulse ≥125, respiratory rate ≥30, systolic BP below 90 mmHg, or temperature below 35 °C or 40 °C and above. Laboratory results play no part in that decision.
What are the PSI class boundaries?
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. The boundaries are inclusive at the top of each class, so a total of exactly 70 is class II and exactly 130 is class IV.
What is the difference between PSI and CURB-65?
PSI uses twenty variables and is better at identifying low-risk patients suitable for outpatient treatment — that is what it was derived for. CURB-65 uses five and is simpler, better known and usable without a blood gas or a chest radiograph. PSI is dominated by age; CURB-65 ignores comorbidity.
What is the main criticism of the PSI?
That it under-weights physiological derangement in young patients. Age supplies most of the total in an older patient and almost none in a young one, and the step-1 class I rule ignores the laboratory panel entirely, so a young patient with severe acidosis and hypoxia can be assigned to the lowest risk class.
Which mortality figure does this page show?
The 30-day mortality Fine et al reported for that class in the MedisGroups validation cohort of 38,039 patients. The derivation and PORT validation cohorts gave different figures — for class III, 2.8% against 0.9% — and all three are in the table on this page.
Related calculators
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):243–50.
- Sligl WI, Marrie TJ. Severe community-acquired pneumonia. Crit Care Clin. 2013 (PMID 23830654).
- Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019;200(7):e45–67.
- Aujesky D, Auble TE, Yealy DM, et al. Prospective comparison of three validated prediction rules for prognosis in community-acquired pneumonia. Am J Med. 2005;118(4):384–92.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.