1PSI Risk Classes & Mortality
| Class | Score | 30-Day Mortality | Recommended Setting |
|---|---|---|---|
| I | Age ≤50 + no comorbidities + no abnormal signs | 0.1% | Outpatient |
| II | ≤70 | 0.6% | Outpatient |
| III | 71–90 | 2.8% | Outpatient or brief inpatient |
| IV | 91–130 | 8.2% | Inpatient |
| V | >130 | 29.2% | Inpatient (consider ICU) |
CAP Antibiotic Recommendations — IDSA/ATS 2019
- Outpatient (Class I–III), previously healthy, no recent antibiotics: Amoxicillin 500 mg TDS × 5 days. Or doxycycline 100 mg BD × 5 days (atypical cover). Azithromycin if low local pneumococcal resistance
- Outpatient with comorbidities (diabetes, heart/lung/liver/renal disease, immunosuppression): Amoxicillin-clavulanate 875/125 mg BD + azithromycin 500 mg OD × 5 days. Or respiratory fluoroquinolone (levofloxacin 750 mg OD × 5 days)
- Inpatient, non-ICU (Class IV): IV β-lactam (ampicillin-sulbactam 3g QID, or ceftriaxone 1–2g OD) + azithromycin 500 mg OD. Or respiratory fluoroquinolone monotherapy
- ICU (Class V, severe CAP): IV β-lactam + IV azithromycin or IV fluoroquinolone. Add anti-MRSA coverage (vancomycin or linezolid) if MRSA risk factors. Add anti-Pseudomonal β-lactam if Pseudomonas risk
PSI vs CURB-65 — Key Differences
- PSI (PORT score): 20 variables, validated in 51,000+ patients, better at identifying LOW-risk patients for outpatient treatment, recommended by IDSA/ATS 2007/2019
- CURB-65: 5 variables (Confusion, Urea, RR, BP, Age ≥65), simpler bedside tool, better for quick HIGH-risk identification, endorsed by BTS guidelines
- Either tool is acceptable per IDSA/ATS 2019. PSI is more conservative (fewer unnecessary admissions); CURB-65 is faster
2About the PSI/PORT Score for Pneumonia
The Pneumonia Severity Index (PSI), also known as the PORT (Patient Outcomes Research Team) score, was developed by Fine et al. (NEJM 1997) from a study of nearly 15,000 patients with community-acquired pneumonia. It remains the most extensively validated CAP severity score and is particularly powerful for identifying low-risk patients safe for outpatient treatment — its primary clinical utility.
PSI class I patients (age <50, no comorbidities, normal vitals) have a 30-day mortality of <0.1% and do not require hospital admission in the absence of social or practical barriers. PSI classes II-III carry low-moderate mortality (0.6-2.8%) and can often be managed with short hospital stays or outpatient treatment with close follow-up. Classes IV-V have high mortality (8.2-29.2%) and require hospitalisation with consideration of ICU admission.
In Indian practice, CAP management is complicated by high rates of antibiotic resistance (ESBL-producing Enterobacteriaceae, multidrug-resistant Klebsiella and Acinetobacter in hospital-acquired pneumonia), atypical pathogen burden (Mycoplasma, Chlamydia, Legionella — particularly in outbreaks), and tropical co-infections (melioidosis in northeast India, scrub typhus). PSI should always be used alongside microbiological results and local resistance patterns rather than as a standalone treatment guide.
3Frequently asked questions
What is a high PSI score?
PSI Class IV (score 91–130) and Class V (score >130) indicate high-risk pneumonia with 30-day mortality of 8.2% and 29.2% respectively. Class IV/V patients require hospital admission, with Class V typically requiring ICU-level care. PSI Classes I–III (score ≤90) are low-risk and can generally be managed as outpatients with close follow-up.
PSI vs CURB-65 — which is better?
Both are validated tools. PSI (PORT score) uses more variables (20 items) and better identifies low-risk patients for outpatient treatment — more conservative, avoids unnecessary admissions. CURB-65 uses only 5 variables and is quicker at the bedside. IDSA/ATS 2019 recommends either tool. PSI is preferred when identifying low-risk patients; CURB-65 is preferred for quick severity assessment in the ED.
Medical disclaimer: This calculator is for educational and clinical decision-support purposes only. It does not replace clinical judgment or specialist consultation. RxMedCalc is not liable for clinical decisions made solely on this tool.