PSI / PORT Score Calculator
The PSI calculator (Pneumonia Severity Index, also known as the PORT score) stratifies adults with community-acquired pneumonia into five risk classes. Enter the patient's age, sex, comorbidities, physical exam findings, and available lab or radiology results to get the total score, risk class (I through V), estimated 30-day mortality, and a disposition recommendation. This tool is based on the validated Fine et al. prediction rule published in the New England Journal of Medicine in 1997.
What is the Pneumonia Severity Index (PSI)?
The Pneumonia Severity Index, often called the PORT score (Patient Outcomes Research Team score), is a validated clinical prediction rule developed by Fine and colleagues and published in the New England Journal of Medicine in 1997. It was designed to help clinicians identify adults with community-acquired pneumonia (CAP) who are at low enough risk to be safely treated as outpatients, reducing unnecessary hospital admissions while ensuring that higher-risk patients receive appropriate inpatient care. The tool assigns weighted points to demographic factors, comorbidities, physical examination findings, and available laboratory or radiographic data, then stratifies the patient into one of five risk classes (I through V), each associated with a known 30-day mortality rate from the original validation cohort.
How the PSI scoring system works
The PSI uses a two-step approach. Step 1 screens for Class I status: patients aged 50 or under who have none of the listed comorbidities and none of the five alarming physical findings (altered mental status, pulse 125 or above, respiratory rate 30 or above, systolic BP below 90 mmHg, or abnormal temperature) are directly classified as Class I with an estimated 30-day mortality of only 0.1%. All other patients proceed to Step 2, where a point total is calculated. Age contributes one point per year, with females receiving a 10-point deduction. Additional points are added for comorbidities such as neoplastic disease (30 points), liver disease (20 points), and congestive heart failure (10 points); for abnormal physical exam findings; and for abnormal laboratory or radiographic results. The highest-weighted individual factors are arterial pH below 7.35 and active neoplasm (30 points each), followed by BUN elevation, hyponatremia, altered mental status, high respiratory rate, and low systolic blood pressure (20 points each). The total score maps to Classes II through V, with 30-day mortalities ranging from 0.6% (Class II) up to 27% (Class V).
Who should be admitted - clinical guidance
Classes I and II are firmly low risk, and guidelines from the Infectious Diseases Society of America and the American Thoracic Society support outpatient treatment for these patients when their social circumstances are adequate. Class III occupies a borderline position: the mortality is still under 1%, but some patients in this range benefit from a short observation stay. Classes IV and V require inpatient admission, and Class V patients should be evaluated for ICU-level care, especially if septic shock, mechanical ventilation, or bilateral infiltrates are present. Clinicians should remember that PSI was designed to identify low-risk patients, not to capture all high-risk cases, so CURB-65 is often used in parallel because it explicitly weights urea and confusion and can flag certain high-risk presentations that PSI might underweight.
PSI versus CURB-65
PSI and CURB-65 are complementary tools rather than competitors. PSI produces a more granular five-class stratification and is especially good at identifying low-risk patients who can safely be treated at home. CURB-65 is simpler (five yes/no criteria scored 0-5) and may be more practical in resource-limited settings or for quick bedside decisions. In practice, many emergency physicians and hospitalists use both: CURB-65 to flag high-risk patients quickly, and PSI to confirm low-risk status before deciding on outpatient discharge. Neither tool should override clinical judgment, and factors such as failure to maintain oral intake, significant hypoxemia corrected by the time of assessment, unreliable follow-up, or rapidly evolving infiltrates on imaging can justify a higher level of care even when the score is reassuring.
PSI / PORT Risk Classes and Outcomes
| Risk Class | Score | 30-Day Mortality | Recommended Disposition |
|---|---|---|---|
| Class I | N/A (screen negative) | 0.1% | Outpatient oral antibiotics |
| Class II | <= 70 | 0.6% | Outpatient oral antibiotics |
| Class III | 71-90 | 0.9% | Outpatient or brief observation |
| Class IV | 91-130 | 9.3% | Inpatient admission |
| Class V | > 130 | 27.0% | Inpatient - consider ICU evaluation |
Based on Fine et al., New England Journal of Medicine, 1997. 30-day mortality rates from the validation cohort.
Frequently asked questions
What does the PSI score measure?
The PSI (Pneumonia Severity Index) estimates 30-day mortality risk in adults with community-acquired pneumonia. It combines demographic information (age, sex), known comorbidities (cancer, liver disease, CHF, stroke, kidney disease), physical examination findings, and available laboratory and imaging results into a single weighted score. The score places the patient into one of five risk classes, each with a characteristic mortality rate and a recommended site of care.
Is a higher PSI score worse?
Yes. A higher PSI score corresponds to a higher risk class and a higher estimated 30-day mortality. Class I and Class II patients have estimated mortalities of 0.1% and 0.6% respectively, while Class V patients have an estimated mortality of 27%. The score increases with age, number of comorbidities, and severity of physical and laboratory abnormalities.
Can I use PSI for all pneumonia patients?
The PSI/PORT score was validated for adults with community-acquired pneumonia (CAP). It should not be used for hospital-acquired or ventilator-associated pneumonia, and it was not designed for patients who are immunocompromised (for example, those with HIV/AIDS, solid organ transplant, or current chemotherapy). The score also does not account for social factors such as the ability to take oral medications reliably, access to follow-up care, or the absence of a safe home environment, all of which may justify admission regardless of the score.
Why does being female lower the PSI score by 10 points?
The 10-point deduction for female sex was an empirical finding from the original Fine et al. derivation cohort: after controlling for other factors, women in that study had slightly lower 30-day mortality than men of the same age. The deduction adjusts for that observed difference, not for any biological mechanism. Some clinicians are cautious about applying this correction universally, since the original cohort may not fully represent all patient populations.
What PSI class is considered safe for outpatient treatment?
Classes I and II are generally considered safe for outpatient management with oral antibiotics, provided the patient can take medications by mouth, has reliable access to follow-up, and has no social factors that warrant admission. Class III patients may also be managed at home or with a brief observation stay, depending on clinical assessment. Classes IV and V require hospital admission, and Class V should prompt consideration of ICU-level evaluation.
What is the difference between PSI and PORT score?
They are the same tool. The PORT score (Patient Outcomes Research Team score) is the official name for the prediction rule developed by Fine and colleagues in 1997, and the Pneumonia Severity Index (PSI) is the common clinical shorthand. Both names refer to the same two-step scoring system with the same weights, classes, and mortality estimates.