PSI - PORT Risk Class Output

The PSI calculator (Pneumonia Severity Index, also called the PORT score) is a clinical decision-support tool that turns age, sex, nursing-home status, five comorbidities, five physical exam findings, and seven lab or imaging values into a 20-item point total. The total places an adult with community-acquired pneumonia into one of five risk classes with the 30-day mortality bands Fine and colleagues reported in 1997. The PSI calculator is the most-validated adult community-acquired pneumonia severity index in the 2019 ATS/IDSA guideline, and it is the same form-and-total approach clinicians use at the bedside to anchor a triage conversation.

• • Emergency-department triage: add a documented risk class to the chart before deciding between observation, a general ward bed, or intensive care.
• • Primary-care conversation: share the risk class and the 30-day mortality band so the admission decision is read against a published reference.
• • Outpatient follow-up planning: review the score a day or two after starting antibiotics to see whether the class is moving with treatment.
• • Quality improvement review: compare admission decisions against the PORT class for a series of CAP cases.

The score is a decision aid, not a treatment order. It does not diagnose pneumonia, prescribe antibiotics, or replace a clinician's review of oxygenation, mental status, or the ability to take oral medication.

When a patient is already admitted and intensive-care decisions are being made, the same first-day clinical picture is also scored with the Apache II Calculator, which is the parallel ICU mortality framework for the same presentation.

The PSI calculator applies the original PORT scoring in three phases. It first checks the class I step-down rule, then it adds points for age, comorbidities, physical exam findings, and lab or imaging results, and finally it places the total into the published risk class.

• agePoints: Patient age in years (men) or age minus 10 (women, clamped at 0).
• nursingHome: Add 10 points when the patient lives in a nursing home or skilled long-term-care facility at presentation.
• comorbidities: Add 30 for active neoplasm, 20 for liver disease, 10 each for CHF, cerebrovascular disease, and renal disease.
• physicalExam: Add 20 for altered mental status, 20 for respiratory rate of 30 or more, 20 for systolic BP below 90, 15 for temperature below 35 degC or 40 degC or higher, 10 for pulse of 125 or more.
• labAndImaging: Add 30 for arterial pH below 7.35, 20 for BUN over 30 mg/dL, 20 for sodium below 130 mEq/L, 10 for glucose of 250 mg/dL or more, 10 for hematocrit below 30 percent, 10 for PaO2 below 60 mmHg, 10 for pleural effusion on chest x-ray.

The 30-day mortality band, the risk class boundaries, and the integer point weights are the same numbers Fine and the PORT team published in 1997.

According to Fine et al., NEJM 1997, the PORT cohort places patients in class I when under 50 with no comorbidity and normal vitals, class II at 70 or fewer, class III 71-90, class IV 91-130, and class V above 130.

The same form-and-total pattern is used in other validated ED risk tools, and the Alvarado Calculator applies it to suspected appendicitis with the same yes/no history inputs and integer point weights, so the two scores travel together on an acute-care chart.

Four concepts keep the score from being read as a black box.

Other validated adult risk tools follow the same evidence ladder.

Reading the score alongside the Aa Gradient Calculator is useful because the same arterial blood gas that produces PaO2 also produces the A-a gradient, and a wide gradient plus a high PSI class is a stronger signal than either finding alone.

The form mirrors the order Fine et al. described: demographics first, comorbidities next, physical exam, then lab and imaging.

1. 1 Enter age and sex: type the patient's age in whole years and select the sex used to apply the female 10-point age offset.
2. 2 Mark the comorbidity block: toggle Yes on the five comorbidities. Active neoplasm adds 30, liver disease adds 20, and CHF, cerebrovascular disease, and renal disease each add 10.
3. 3 Add altered mental status if present: select Yes if the patient is newly disoriented, stuporous, comatose, or otherwise acutely changed from baseline.
4. 4 Enter the first measured vital signs: type the first respiratory rate, systolic blood pressure, temperature, and pulse.
5. 5 Enter the admission lab and imaging values: type the arterial pH, BUN, sodium, glucose, hematocrit, and PaO2 from the first set of labs, and toggle Yes if pleural effusion is visible on the admission chest x-ray.
6. 6 Read the result together: use the risk class and the 30-day mortality band to inform the next step, and pair them with the disposition hint.

A 65-year-old man with CHF and normal labs except PaO2 70 scores 85, placing him in class III with 30-day mortality around 0.9 percent and an outpatient-with-close-follow-up hint.

Reading the same arterial blood gas through the Acid Base Calculator confirms the bicarbonate and pH interpretation, so the same admission labs answer more than one question.

Using the score the way the original PORT cohort intended gives several practical benefits over a single set of vital signs or a single lab.

• • Documented PORT total: the original 20-item point total with the published integer weights, read alongside the Fine et al. 1997 paper.
• • Risk class I to V with original mortality bands: the calculator places the total into one of the five published risk classes.
• • Class I step-down for low-risk adults: an adult under 50 with no comorbidity and normal vitals is placed in class I without running the full lab set.
• • Transparent sub-totals: the result panel shows the age, comorbidity, physical exam, and lab sub-totals so it is clear which block is driving the class.
• • Disposition hint tied to the class: the calculator pairs the risk class with a starting disposition (outpatient, outpatient with close follow-up, inpatient, or inpatient with ICU consideration).
• • Aligned with the 2019 ATS/IDSA guideline: the score and the class boundaries match the 2019 ATS/IDSA community-acquired pneumonia guideline.

The ANC Calculator reads the absolute neutrophil count from a routine CBC so the same admission labs answer more than one question.

The result depends on a small set of assumptions and thresholds. A few changes to the input set can move a patient from one risk class to the next, especially near the 70, 90, and 130 boundaries.

• • The score is a decision aid for adults with community-acquired pneumonia, not a pediatric, pregnancy, or immune-compromised tool.
• • A young adult with chronic liver disease and a temperature of 40 degC should be scored with the full point total, not skipped to class I.
• • The score depends on the first measured values; a volume-resuscitated or antipyretic-pretreated patient will score lower than at presentation.

Reading the score as decision support rather than diagnosis keeps the conversation anchored to the patient in front of the clinician. The PSI calculator pairs the class with a clear disposition hint so the next step is read in the same glance.

According to ATS/IDSA 2019 CAP guideline, the Pneumonia Severity Index is the recommended severity tool alongside CURB-65.

According to Fine et al., MEDLINE 1997, 30-day mortality in the PORT cohort was 0.1 percent in class I, 0.6 percent in class II, 0.9 percent in class III, 4.0 to 8.2 percent in class IV, and 13.5 to 31.1 percent in the highest class.