Pneumonia Severity Index has similar sensitivity to CURB-65
A more detailed assessment using 20 parameters called the Pneumonia Severity Index (PSI) was derived and validated in separate cohorts (TABLE 2).2 When compared with CURB-65 and CRB-65, the PSI has similar sensitivity and specificity in predicting 30-day mortality.3 All 3 predictive rules had high negative predictive values for mortality but a low positive predictive value at all cutoff points.
Larger proportions of patients were identified as low-risk by PSI (47.2%) and CURB-65 (43.3%) than by CRB-65 (12.6%). Therefore PSI and CURB-65 are much more helpful in identifying patients who could be treated in the outpatient setting.
TABLE 2
Pneumonia Severity Index
| CHARACTERISTIC | POINTS ASSIGNED | |
| Demographic factors | ||
| Age, men | Age in years | |
| Age, women | Age in years –10 | |
| Nursing home resident | +10 | |
| Coexisting illnesses | ||
| Neoplastic disease | +30 | |
| Liver disease | +20 | |
| Congestive heart failure | +10 | |
| Cerebrovascular disease | +10 | |
| Renal disease | +10 | |
| Physical examination findings | ||
| Altered mental status | +20 | |
| Respiratory rate ≥30/min | +20 | |
| Systolic blood pressure <90 mm Hg | +20 | |
| Temperature <35°C (95°F) or ≥40°C (104°F) | +15 | |
| Pulse ≥125 beats/min | +10 | |
| Laboratory and radiographic findings | ||
| Arterial blood pH <7.35 | +30 | |
| Blood urea nitrogen level ≥30 mg/dL | +20 | |
| Sodium level <130 mmol/L | +20 | |
| Glucose level ≥250 mg/dL | +10 | |
| Hematocrit <30% | +10 | |
| Partial pressure of arterial O2 <60 mm Hg or O2 saturation <90% on pulse oximetry | +10 | |
| Pleural effusion | +10 | |
| RISK CLASS | POINTS | 30-DAY MORTALITY |
| I | 0–50 | 0.1%–0.4% |
| II | 51–70 | 0.6%–0.7% |
| III | 71–90 | 0.9%–2.8% |
| IV | 91–130 | 8.3%–9.3% |
| V | >130 | 27.0%–31.1% |
| Patients in classes I, II, and III can be managed on an outpatient basis; patients in classes IV and V should be hospitalized. | ||
| Source: Fine et al 1997.2 | ||
Recommendations from others
The 2007 Infectious Diseases Society of America (IDSA) and American Thoracic Society (ATS), in their Consensus Guidelines on the Management of Community-Acquired Pneumonia,4 concluded that severity-of-illness scores, such as the CURB-65 or PSI, can be used to identify patients with CAP who may be candidates for outpatient treatment (evidence level I by IDSA/ATS rating).
The guidelines recommend that objective criteria or scores always be supplemented with physician determination of subjective factors, including the ability to safely and reliably take oral medication and the availability of outpatient support resources. Also, CURB-65 is more suitable than PSI for use in the emergency department because of its simplicity of application and ability to identify low-risk patients (evidence level II).4