Pneumonia severity index: PSI/PORT points and classes (Fine 1997)

The pneumonia severity index, also called the PSI or PORT score, places adults with community-acquired pneumonia into five risk classes. It works in two steps: a quick check that can put someone straight into Class I, and then a points table for everyone else. This calculator follows the Fine 1997 rule and returns the point total and the class.

Not a medical device. Not a diagnosis or dosing recommendation.

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Infection and VTE calculators
Fine MJ et al. · 1997
The PSI/PORT formula
Worked examples
Frequently asked questions

What is the pneumonia severity index?

Fine and colleagues developed the rule to pick out patients with community-acquired pneumonia at low risk. Step 1 asks whether the person is 50 or younger, has none of five listed conditions, is alert and has vital signs inside set limits. If so, they're Class I. If not, step 2 adds points for age, sex, conditions, examination findings and test results, and the total sets Class II to V.

All conditions and findings are supplied by the caller.

The PSI/PORT formula

Step 1 (Class I): age 50 or younger
                  and no neoplastic, liver, heart failure,
                      cerebrovascular or renal disease
                  and no altered mental status
                  and HR < 125, RR < 30, SBP ≥ 90, 35 ≤ temp < 40

Step 2 (points):  age (men) or age − 10 (women)
                  + nursing home 10 + neoplastic 30 + liver 20
                  + heart failure 10 + cerebrovascular 10 + renal 10
                  + altered mental status 20 + RR ≥ 30 20 + SBP < 90 20
                  + temp < 35 or ≥ 40 15 + HR ≥ 125 10
                  + pH < 7.35 30 + BUN ≥ 30 20 + sodium < 130 20
                  + glucose ≥ 250 10 + hematocrit < 30 10
                  + PaO2 < 60 10 + pleural effusion 10

Class II ≤ 70, III 71-90, IV 91-130, V > 130

Exact expression the calculator uses:

PSI/PORT two-step (Fine 1997): Class I if age<=50 and no neoplastic, liver, CHF, cerebrovascular, renal, AMS and HR<125, RR<30, SBP>=90, temp>=35 and <40; else Table 2 points: age (men) or age-10 (women) + nursing_home 10 + neoplastic 30 + liver 20 + CHF 10 + cerebrovascular 10 + renal 10 + AMS 20 + RR>=30 20 + SBP<90 20 + (temp<35 or >=40) 15 + HR>=125 10 + pH<7.35 30 + BUN>=30 20 + Na<130 20 + glucose>=250 10 + Hct<30 10 + PaO2<60 10 + pleural_effusion 10; class I from step 1 else 2 if <=70, 3 if 71-90, 4 if 91-130, 5 if >130

Inputs

Input	Unit or values	Points in step 2
`age`, `sex`	years; female or male	age, or age − 10 for women
`nursing_home`	true or false	10
`neoplastic`	true or false	30
`liver_disease`	true or false	20
`chf`	true or false	10
`cerebrovascular`	true or false	10
`renal_disease`	true or false	10
`altered_mental_status`	true or false	20
`respiratory_rate`	breaths/min	20 if 30 or more
`systolic_mm_hg`	mm Hg	20 if below 90
`temperature_c`	°C	15 if below 35 or 40 or more
`heart_rate_bpm`	beats/min	10 if 125 or more
`arterial_ph`	pH	30 if below 7.35
`bun_mg_dl`	mg/dL	20 if 30 or more
`sodium_mmol_l`	mmol/L	20 if below 130
`glucose_mg_dl`	mg/dL	10 if 250 or more
`hematocrit_percent`	%	10 if below 30
`pao2_mm_hg`	mm Hg	10 if below 60
`pleural_effusion`	true or false	10

How the calculation works

Step 1. If the person is 50 or younger, has none of the five conditions or altered mental status, and has a heart rate below 125, respiratory rate below 30, systolic pressure of 90 or more and a temperature from 35 up to but not including 40, the class is 1.
Step 2. Otherwise add the points: age for men, age minus 10 for women, plus the points for each item present.
Set the class from the total: 70 or less is 2, 71 to 90 is 3, 91 to 130 is 4 and above 130 is 5.

The calculator always returns the point total, even for Class I, so you can see it. The oxygenation item here is PaO2 below 60 mm Hg; the calculator has no oxygen saturation input.

Worked examples

These use Magent's own expected values for the calculator. Unless stated, the inputs are normal: heart rate 80, respiratory rate 16, systolic 120, temperature 37.0 °C, pH 7.40, BUN 14, sodium 140, glucose 90, hematocrit 42, PaO2 90 and no listed conditions.

Example 1: a 45-year-old man with normal findings

Age 45 is 50 or younger, no conditions are present and the vital signs are inside the step 1 limits.
The points total is 45, the age.
PSI class 1.

Example 2: an 80-year-old man with normal findings

Age 80 is over 50, so step 2 applies.
Points: age 80, nothing else.
80 falls in 71 to 90.
PSI class 3.

Example 3: an 80-year-old man with cancer, confusion, fast breathing and low pressure

Step 2 applies.
80 + 30 + 20 + 20 + 20 = 170 (age, neoplastic disease, altered mental status, respiratory rate 30, systolic 89).
170 is above 130.
PSI class 5.

History of the pneumonia severity index

Fine and colleagues published "A prediction rule to identify low-risk patients with community-acquired pneumonia" in the New England Journal of Medicine in 1997. The two steps and the point table the calculator uses come from that paper.

When it's used

When an adult has community-acquired pneumonia and a structured risk class is wanted alongside clinical judgement.

Where it's used

Emergency departments, admission units and research on pneumonia.

Who uses it

Emergency physicians, hospital doctors and researchers. The calculator handles the two steps and the points.

Limits of the calculation

Age carries a lot of weight, so older people reach higher classes even with few other findings.
It needs many test results. Missing values can't be guessed by the calculator.
Oxygenation is entered as PaO2; there's no oxygen saturation input.
The class describes risk in the study population. The calculator doesn't advise on where someone should be cared for.
This page doesn't say what a class means for a particular person.

Clinical decisions belong to a qualified clinician who knows the patient.

CURB-65 uses five items, including urea.
CRB-65 drops the urea item, so it needs no blood tests.

Glossary

Community-acquired pneumonia: pneumonia that starts outside hospital.
BUN: blood urea nitrogen, in mg/dL.
PaO2: the oxygen level in arterial blood, in mm Hg.
Altered mental status: new confusion or reduced alertness.

Common mistakes

Forgetting the 10-point reduction for women.
Skipping step 1. Someone who meets every step 1 condition is Class I whatever the points.
Entering glucose in mmol/L. The points table uses mg/dL.

Source

Fine MJ, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997;336(4):243-250. DOI: 10.1056/NEJM199701233360402. PMID: 8995086

Frequently asked questions

How is the pneumonia severity index calculated?

First check the step 1 conditions for Class I. If they aren't all met, add the step 2 points and read the class from the total.

What are the PSI classes?

Class I comes from step 1. Then 70 points or less is II, 71 to 90 III, 91 to 130 IV and above 130 V.

Why does the calculator return points for a Class I patient?

It always returns the total for transparency. The class still comes from step 1.

Is PSI the same as PORT?

Yes. PSI and PORT are two names for the same Fine 1997 rule.