Pneumonia Severity Index (PSI/PORT) Calculator
Calculate the formal two-step PSI/PORT score and class for adult community-acquired pneumonia, with historical risk and site-of-care context.
Content updated: View sources
QuickMedCalc is developed and maintained by an independent developer. Medical content is not independently reviewed by a physician.
Formula and medical content are based on the references listed on this page. See sources, About, and Sources and Review Process.
About
The Pneumonia Severity Index (PSI/PORT) calculator applies the formal Fine 1997 two-step prognostic classification to adults with an established community-acquired pneumonia (CAP) diagnosis, using findings from the same initial acute presentation. In the formal Step 1 route, a completed age of 50 years or younger plus ten explicit absent findings can produce Class I; all other routes require the formal Step 2 items. The historical male and female coefficients are Step 2 model terms, not a complete modern sex or gender classification. [1, 2]
This page calculates only the values explicitly submitted. It does not diagnose pneumonia, identify a pathogen, validate records, imaging, oxygenation, laboratory authenticity, sepsis, shock, respiratory failure, or a patient’s exact mortality probability. PSI class and historical point total are reference outputs, not automatic antibiotic, discharge, admission, ICU, or other treatment decisions. Current U.S. guidance uses PSI to supplement clinical judgment in site-of-care assessment, while local systems may use different tools. [3, 6]
Formula
Interpretation
Original cohort mortality context — not a personal prediction
| PSI class | Formal route | Observed 30-day mortality | Required interpretation |
|---|---|---|---|
| I | Step 1 | 0.1–0.4% | Historical cohort context only |
| II | Step 2 ≤70 | 0.6–0.7% | Not automatic outpatient eligibility |
| III | Step 2 71–90 | 0.9–2.8% | Not an automatic observation/admission order |
| IV | Step 2 91–130 | 8.2–9.3% | Not an automatic ICU rule |
| V | Step 2 >130 | 27.0–31.1% | Not an individual prediction |
- PSI class
- I
- Formal route
- Step 1
- Observed 30-day mortality
- 0.1–0.4%
- Required interpretation
- Historical cohort context only
- PSI class
- II
- Formal route
- Step 2 ≤70
- Observed 30-day mortality
- 0.6–0.7%
- Required interpretation
- Not automatic outpatient eligibility
- PSI class
- III
- Formal route
- Step 2 71–90
- Observed 30-day mortality
- 0.9–2.8%
- Required interpretation
- Not an automatic observation/admission order
- PSI class
- IV
- Formal route
- Step 2 91–130
- Observed 30-day mortality
- 8.2–9.3%
- Required interpretation
- Not an automatic ICU rule
- PSI class
- V
- Formal route
- Step 2 >130
- Observed 30-day mortality
- 27.0–31.1%
- Required interpretation
- Not an individual prediction
These are observations from the original derivation and validation cohorts, not a modern universal calibration or an individual patient probability. Discrimination and calibration are different: a model can preserve rank ordering while over- or under-estimating absolute risk in another era, region, treatment setting, or population. External validation therefore may require study-specific recalibration. [1, 8]
The 2019 ATS/IDSA guideline describes PSI as a U.S. site-of-care aid used with clinical judgment; PSI is not an ICU severity tool. NICE NG250 uses CRB65 in primary/community assessment and CURB65 in hospital assessment, so PSI is not the only current international pathway. [3, 6]
PSI / PORT steps, point values, and clinical boundaries
Formal Step 1 Class I screen
Step 1 is a gate, not a low numeric score. It requires age ≤50 and all ten comorbidity and examination entries explicitly absent. It does not use laboratory or imaging fields. Unknown, blank, or a known abnormality cannot be treated as absent; Class I also does not prove no pneumonia or automatic discharge eligibility. [1, 2, 3]
| Domain | Required finding | Important limitation |
|---|---|---|
| Age | ≤50 completed years | Age 51 or older enters Step 2 |
| Neoplastic disease | Absent | Do not infer from an unreviewed symptom |
| Liver disease | Absent | Documented chronic liver disease is a Step 1 item |
| Congestive heart failure | Absent | Known instability still needs clinical assessment |
| Cerebrovascular disease | Absent | History is not inferred from age |
| Renal disease | Absent | Use the formal historical item definition |
| Altered mental status | Absent | Known chronic baseline deficit is not automatically new |
| Respiratory rate | <30/min | ≥30/min prevents the Step 1 route |
| Systolic blood pressure | ≥90 mmHg | <90 mmHg prevents the Step 1 route |
| Temperature | ≥35°C / 95°F and <40°C / 104°F | Outside this interval prevents the Step 1 route |
| Pulse | <125/min | ≥125/min prevents the Step 1 route |
- Domain
- Age
- Required finding
- ≤50 completed years
- Important limitation
- Age 51 or older enters Step 2
- Domain
- Neoplastic disease
- Required finding
- Absent
- Important limitation
- Do not infer from an unreviewed symptom
- Domain
- Liver disease
- Required finding
- Absent
- Important limitation
- Documented chronic liver disease is a Step 1 item
- Domain
- Congestive heart failure
- Required finding
- Absent
- Important limitation
- Known instability still needs clinical assessment
- Domain
- Cerebrovascular disease
- Required finding
- Absent
- Important limitation
- History is not inferred from age
- Domain
- Renal disease
- Required finding
- Absent
- Important limitation
- Use the formal historical item definition
- Domain
- Altered mental status
- Required finding
- Absent
- Important limitation
- Known chronic baseline deficit is not automatically new
- Domain
- Respiratory rate
- Required finding
- <30/min
- Important limitation
- ≥30/min prevents the Step 1 route
- Domain
- Systolic blood pressure
- Required finding
- ≥90 mmHg
- Important limitation
- <90 mmHg prevents the Step 1 route
- Domain
- Temperature
- Required finding
- ≥35°C / 95°F and <40°C / 104°F
- Important limitation
- Outside this interval prevents the Step 1 route
- Domain
- Pulse
- Required finding
- <125/min
- Important limitation
- ≥125/min prevents the Step 1 route
Formal Step 2 point table
Once Step 1 does not apply, every Step 2 item must be explicitly present, absent, or unknown. Hypoxemia is one ten-point item even when more than one qualifying observation is present; the historical binary demographic coefficient is not a complete modern biological classification. [1, 2]
| Category | Factor | Points | Definition or boundary |
|---|---|---|---|
| Demographics | Historical male coefficient | Age or age − 10 | Male base = age; female base = age − 10 |
| Demographics | Nursing-home residence | 10 | Add once when present |
| Comorbidity | Neoplastic disease | 30 | Formal historical item |
| Comorbidity | Liver disease | 20 | Formal historical item |
| Comorbidity | Congestive heart failure | 10 | Formal historical item |
| Comorbidity | Cerebrovascular disease | 10 | Formal historical item |
| Comorbidity | Renal disease | 10 | Formal historical item |
| Examination | Altered mental status | 20 | Initial examination finding |
| Examination | Respiratory rate ≥30/min | 20 | Threshold is inclusive |
| Examination | Systolic BP <90 mmHg | 20 | Threshold is strictly below 90 |
| Examination | Temperature <35°C / <95°F or ≥40°C / ≥104°F | 15 | Either extreme adds one item |
| Examination | Pulse ≥125/min | 10 | Threshold is inclusive |
| Laboratory | Arterial pH <7.35 | 30 | Initial arterial measurement |
| Laboratory | BUN ≥30 mg/dL or urea ≥11 mmol/L | 20 | Use the analyte and unit reported by the laboratory |
| Laboratory | Sodium <130 mmol/L | 20 | Initial serum sodium |
| Laboratory | Glucose ≥250 mg/dL or ≥14 mmol/L | 10 | Initial serum glucose |
| Laboratory | Hematocrit <30% | 10 | Initial hematocrit |
| Imaging/oxygenation | Hypoxemia | 10 | PaO₂ <60 mmHg / <8 kPa, SpO₂ <90%, or pre-admission intubation; add once |
| Imaging | Pleural effusion | 10 | Initial chest imaging |
- Category
- Demographics
- Factor
- Historical male coefficient
- Points
- Age or age − 10
- Definition or boundary
- Male base = age; female base = age − 10
- Category
- Demographics
- Factor
- Nursing-home residence
- Points
- 10
- Definition or boundary
- Add once when present
- Category
- Comorbidity
- Factor
- Neoplastic disease
- Points
- 30
- Definition or boundary
- Formal historical item
- Category
- Comorbidity
- Factor
- Liver disease
- Points
- 20
- Definition or boundary
- Formal historical item
- Category
- Comorbidity
- Factor
- Congestive heart failure
- Points
- 10
- Definition or boundary
- Formal historical item
- Category
- Comorbidity
- Factor
- Cerebrovascular disease
- Points
- 10
- Definition or boundary
- Formal historical item
- Category
- Comorbidity
- Factor
- Renal disease
- Points
- 10
- Definition or boundary
- Formal historical item
- Category
- Examination
- Factor
- Altered mental status
- Points
- 20
- Definition or boundary
- Initial examination finding
- Category
- Examination
- Factor
- Respiratory rate ≥30/min
- Points
- 20
- Definition or boundary
- Threshold is inclusive
- Category
- Examination
- Factor
- Systolic BP <90 mmHg
- Points
- 20
- Definition or boundary
- Threshold is strictly below 90
- Category
- Examination
- Factor
- Temperature <35°C / <95°F or ≥40°C / ≥104°F
- Points
- 15
- Definition or boundary
- Either extreme adds one item
- Category
- Examination
- Factor
- Pulse ≥125/min
- Points
- 10
- Definition or boundary
- Threshold is inclusive
- Category
- Laboratory
- Factor
- Arterial pH <7.35
- Points
- 30
- Definition or boundary
- Initial arterial measurement
- Category
- Laboratory
- Factor
- BUN ≥30 mg/dL or urea ≥11 mmol/L
- Points
- 20
- Definition or boundary
- Use the analyte and unit reported by the laboratory
- Category
- Laboratory
- Factor
- Sodium <130 mmol/L
- Points
- 20
- Definition or boundary
- Initial serum sodium
- Category
- Laboratory
- Factor
- Glucose ≥250 mg/dL or ≥14 mmol/L
- Points
- 10
- Definition or boundary
- Initial serum glucose
- Category
- Laboratory
- Factor
- Hematocrit <30%
- Points
- 10
- Definition or boundary
- Initial hematocrit
- Category
- Imaging/oxygenation
- Factor
- Hypoxemia
- Points
- 10
- Definition or boundary
- PaO₂ <60 mmHg / <8 kPa, SpO₂ <90%, or pre-admission intubation; add once
- Category
- Imaging
- Factor
- Pleural effusion
- Points
- 10
- Definition or boundary
- Initial chest imaging
How the two-step calculator works
- Uses age and the ten Step 1 findings first.
- Returns Class I without a sex coefficient when age is 50 or younger and every Step 1 finding is absent.
- Otherwise requires the historical Step 2 sex coefficient and all eight additional findings.
- Treats unknown as not-calculable rather than absent or zero.
- Returns the class, any Step 2 total, and a submitted-value audit.
It does not read a record, diagnose CAP, validate a chest image, identify a pathogen, calculate CURB-65/CRB65 or severe-CAP criteria, choose antibiotics, or decide discharge, admission, or ICU care. [1, 3]
PSI and related CAP tools
| Tool | Intended setting | Inputs | Primary question | Why not interchangeable |
|---|---|---|---|---|
| PSI / PORT | Adult established CAP | Two-step demographic, comorbidity, exam, laboratory and imaging items | Historical prognostic class and site-of-care aid | This page only |
| CURB-65 | CAP severity context | Confusion, urea, RR, BP, age | Different compact score | Fewer variables and different route |
| CRB65 | NICE primary/community context | Confusion, RR, BP, age | Different international pathway | No urea and not PSI |
| ATS/IDSA severe CAP criteria | Higher-intensity/ICU assessment | Major and minor physiologic criteria | Severe CAP support needs | Not a PSI class or score conversion |
- Tool
- PSI / PORT
- Intended setting
- Adult established CAP
- Inputs
- Two-step demographic, comorbidity, exam, laboratory and imaging items
- Primary question
- Historical prognostic class and site-of-care aid
- Why not interchangeable
- This page only
- Tool
- CURB-65
- Intended setting
- CAP severity context
- Inputs
- Confusion, urea, RR, BP, age
- Primary question
- Different compact score
- Why not interchangeable
- Fewer variables and different route
- Tool
- CRB65
- Intended setting
- NICE primary/community context
- Inputs
- Confusion, RR, BP, age
- Primary question
- Different international pathway
- Why not interchangeable
- No urea and not PSI
- Tool
- ATS/IDSA severe CAP criteria
- Intended setting
- Higher-intensity/ICU assessment
- Inputs
- Major and minor physiologic criteria
- Primary question
- Severe CAP support needs
- Why not interchangeable
- Not a PSI class or score conversion
The 2019 ATS/IDSA guideline recommends PSI rather than CURB-65 as a supplement to clinical judgment for U.S. site-of-care assessment; NICE uses CRB65/CURB65 in a different pathway, and severe-CAP criteria address ICU-level questions. [3, 6, 7]
Current guideline context
The 2019 joint ATS/IDSA adult CAP guideline remains the principal U.S. context for PSI site-of-care use. The newer ATS-only focused CAP guideline addresses lung-ultrasound diagnosis, antibacterial therapy in respiratory-virus-positive CAP, antibiotic duration, and systemic corticosteroids; it did not rewrite the Fine PSI/PORT algorithm or the 2019 site-of-care recommendation. IDSA has not endorsed it as a whole because of disagreement around some antibacterial-treatment recommendations, so this page does not present it as a new joint ATS/IDSA PSI update. NICE NG250 is a separate current UK framework using CRB65/CURB65 rather than PSI. [3, 4, 5, 6]
Worked examples from the validated implementation
- Formal Class I: age 50, no sex coefficient, all ten Step 1 findings absent, and Step 2 blank → Class I, Step 1, no point total. Age 51 cannot use this route.
- Class II boundary: a validated Step 2 total of 70 is Class II; the same route at 71 is Class III.
- Mixed vector: age 65 with the historical female coefficient (base 55), nursing-home residence, heart failure, respiratory rate ≥30, BUN/urea threshold present, and pleural effusion → 125 points, Class IV.
- Unknown: an unknown BUN/urea item returns not-calculable with no class or point total while known items remain in the audit.
These are arithmetic and route examples generated from the validated implementation, not patient-level probabilities or management instructions. [1, 2]
Historical mortality and calibration
Original class ranges retain historical ordering and context, but absolute risk can change with era, region, treatment, admission thresholds, and case mix. Flanders et al. found good discrimination but poor calibration in an external cohort and described study-specific recalibration. Calibration is not the same as discrimination, and this page does not generate a modern individualized mortality estimate. [1, 8]
Important limitations
Known hypoxemia, acidosis, or other major abnormality or instability still requires independent assessment. Interpretation can also be limited by oxygenation or respiratory support, sepsis, shock, respiratory failure, rapid deterioration, multilobar disease, pleural complications, major comorbidity instability, frailty, function, cognition, oral intake, adherence, social support, pregnancy, childhood, HIV, transplant, chemotherapy, severe immunosuppression, HAP, VAP, changing treatment response, or an evolving clinical state. PSI may understate a young patient with severe physiology; a low class is not a safe-discharge rule, and a high class is not an automatic ICU rule. Do not wait for an online calculator in an unstable or emergency situation. [3, 4, 6]
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;336:243–250. PMID 8995086. DOI 10.1056/NEJM199701233360402.
- Mandell LA, Bartlett JG, Dowell SF, et al. Update of Practice Guidelines for the Management of Community-Acquired Pneumonia in Immunocompetent Adults. Clin Infect Dis. 2003;37(11):1405–1433. PMID 14614663. DOI 10.1086/380488.
- Metlay JP, Waterer GW, Long AC, et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. Am J Respir Crit Care Med. 2019;200(7):e45–e67. PMID 31573350. PMCID PMC6812437. DOI 10.1164/rccm.201908-1581ST.
- Jones BE, et al. Diagnosis and Management of Community-acquired Pneumonia: An Official American Thoracic Society Clinical Practice Guideline. Am J Respir Crit Care Med. 2026;212(1):24–44. PMID 40679934. DOI 10.1164/rccm.202507-1692ST.
- Infectious Diseases Society of America. Antibiotics in community-acquired pneumonia when respiratory viruses are detected: Adding more fuel to the fire? Science Speaks. 2026. IDSA reports that it did not endorse the recent ATS guideline; this source is cited only for that organizational-position context.
- NICE. Pneumonia: diagnosis and management (NG250). Recommendations, published 2 September 2025.
- 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):384–392. PMID 15808136. DOI 10.1016/j.amjmed.2005.01.006.
- Flanders WD, Tucker G, Krishnadasan A, et al. Validation of the Pneumonia Severity Index: Importance of Study-Specific Recalibration. J Gen Intern Med. 1999;14(6):333–340. PMID 10354252. PMCID PMC1496595. DOI 10.1046/j.1525-1497.1999.00351.x.
FAQ
The Fine 1997 PSI/PORT rule classifies adults with diagnosed community-acquired pneumonia into original-cohort 30-day mortality-risk classes. It can supplement clinical judgment for initial inpatient versus outpatient site-of-care assessment. It does not diagnose pneumonia, provide an individual exact mortality probability, select antibiotics, or determine treatment.
PSI/PORT uses a larger two-step set of demographic, comorbidity, examination, laboratory, and imaging findings than CURB-65. The 2019 joint ATS/IDSA adult CAP guideline recommends PSI rather than CURB-65 to supplement clinical judgment for site-of-care assessment. Neither tool replaces a full assessment.
The formal first step assigns Class I when an adult is 50 years or younger and has none of the five specified comorbidities or five abnormal examination findings. Laboratory testing is not part of that first-step screen, but a known abnormal laboratory or imaging result must still inform clinical judgment and should not be ignored because Step 1 was met.
No. A blank item means the submission is incomplete. Present and absent are explicit findings; Unknown means the item was considered but cannot be established. Unknown is never treated as absent and produces a no-class audit rather than a partial PSI class. Step 1 can formally proceed without laboratory or imaging data, but known abnormalities remain clinically relevant.
No. A low class is not proof of no pneumonia, no deterioration risk, or automatic outpatient suitability. Hypoxemia, sepsis, inability to take oral therapy, pregnancy, decompensated illness, adherence, and social support can override a low-risk classification. PSI is one input to clinical judgment, not a disposition order.
The formal Step 1 Class I route does not use a sex coefficient. When Step 2 is required, the original Fine model assigns age in years for the historical male coefficient and age minus 10 for the historical female coefficient. This calculator reproduces those original coefficients without inferring which one applies outside those historical categories; the variable is not a complete modern biological or identity classification.
Sources: [1]
PSI was developed in general adult CAP populations, principally in immunocompetent adults. HIV, transplant, chemotherapy, severe immunosuppression, pregnancy, and other special situations require relevant specialized guidance and additional clinical factors. This does not make PSI automatically invalid, but it cannot alone determine management in these settings.
Age 50 or younger may use formal Step 1 without a sex coefficient only when all ten Step 1 items are absent. At age 51 and above, the original PSI calculation proceeds to Step 2 and requires the historical male or female coefficient even when those ten items are absent.
Sources: [1]
It is a documented abnormal mental-status finding at the initial CAP presentation. It is not automatically inferred from age, sedation, a single screening score, or a later change in condition.
Sources: [2]
The formal items are respiratory rate at least 30/min, systolic blood pressure below 90 mmHg, temperature below 35°C or at least 40°C, and pulse at least 125/min; altered mental status is the remaining physical-examination item in the ten-item first step.
Sources: [2]
No. PSI/PORT does not identify an organism, select antimicrobial therapy, or replace diagnostic testing and the applicable CAP pathway.
Sources: [3]
PSI is one formal prognostic classification. It does not measure every practical or clinical reason that a person may require observation or inpatient support, including inability to take oral therapy or insufficient support at home.
Sources: [3]
Related Calculators
CURB-65
Calculate the five CURB-65 criteria for adult community-acquired pneumonia using confusion, urea or BUN, respiratory rate, systolic and diastolic blood pressure, and age, with current NICE hospital risk groups.
APACHE II
Reproduce the 1985 adult general-ICU APACHE II severity score from worst first-24-hour physiology, age and defined chronic-health points.
SOFA Score
Calculate the original Classic SOFA-1 score from raw clinical values across six organ systems in one defined 24-hour window, with an optional comparable-baseline change.
Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.