| Measure | Score |
| Patient age yrs | |
| Male patient | +10 |
| History of cancer | +30 |
| History of heart failure | +10 |
| History of chronic lung disease | +10 |
| Heart rate ≥110 beats·min−1 | +20 |
| Systolic blood pressure <100 mmHg | +30 |
| Respiratory rate ≥30 breaths·min−1 | +20 |
| Temperature <36°C/96.8°F | +20 |
| Altered mental status | +60 |
| O2 saturation <90% | +20 |
The PESI risk score is calculated by starting with the patient’s age and adding additional points for any factors present as noted above. The patients are divided into five risk classes based upon the point total as follows: class I, <65 points; class II, 66–85 points; class III, 86–105 points; class IV, 106–125 points; class V, >126 points. Reproduced and modified from [5] with permission from the publisher.