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Printed on 7/19/2026
For informational purposes only. This is not medical advice.
CRB-65 is a simplified pneumonia risk score derived from CURB-65 that removes the blood urea (BUN) requirement. It uses four bedside variables: Confusion, Respiratory rate, Blood pressure, and age 65 or older. It is especially useful in primary care, urgent care, and prehospital settings where immediate labs are not available.
Formula: CRB-65 = Confusion + Respiratory rate ≥30 + low blood pressure + age ≥65 (0-4 total).
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Assess four items that can be evaluated at the bedside without any laboratory testing: Confusion (new disorientation to person, place, or time), Respiratory rate ≥30 breaths per minute, Blood pressure below threshold (systolic <90 mmHg OR diastolic ≤60 mmHg), and Age ≥65 years. Each criterion present scores 1 point.
Add up applicable items. The total CRB-65 score ranges from 0 to 4. Because BUN is excluded (unlike CURB-65), the maximum achievable score is 4, not 5. Calculate the score while evaluating the patient — it takes under 30 seconds to complete.
CRB-65 score 0 = low mortality risk (<1%) — outpatient oral antibiotic treatment appropriate; CRB-65 score 1–2 = moderate risk — consider hospitalization or urgent face-to-face evaluation with close follow-up; CRB-65 score 3–4 = high mortality risk — immediate hospital admission required, consider ICU for score 4. Always supplement with SpO2 measurement.
Family medicine, urgent care, general practitioners
CRB-65 is specifically designed for settings where BUN is not immediately available. In primary care and urgent care settings, CRB-65 score 0 enables safe same-day discharge with oral antibiotics; scores 1–2 prompt a call to the ED or same-day hospital evaluation; score 3–4 triggers immediate 999/911 or emergency referral.
Emergency physicians, nurses
In emergency settings where lab results are pending, CRB-65 enables immediate risk stratification while awaiting BUN results. Once BUN returns, CURB-65 provides a more complete picture. CRB-65 is the appropriate initial triage tool in the first minutes after patient presentation.
All clinicians managing CAP
CRB-65 score 0 identifies patients with very low 30-day mortality risk (<1%). These patients can safely receive outpatient oral amoxicillin (with or without a macrolide for atypical coverage) without hospitalization, reducing unnecessary admissions and healthcare-associated complications.
All prescribers
CRB-65 score directly guides antibiotic intensity: Score 0 = oral amoxicillin ± macrolide (outpatient); Score 1–2 = consider IV beta-lactam + macrolide or respiratory fluoroquinolone (ward); Score 3–4 = IV broad-spectrum antibiotics including Legionella and MRSA coverage assessment (high-acuity setting).
All clinicians
CRB-65 provides an objective, easy-to-communicate risk estimate. Explaining to patients that a score of 0 means very low risk enables shared decision-making about outpatient treatment, while higher scores provide evidence for recommending hospitalization even to patients who feel 'not that sick.'
The only difference between CRB-65 and CURB-65 is the absence of the BUN (blood urea nitrogen) criterion. CRB-65 maximum score is 4 (vs 5 for CURB-65). When laboratory results are available in hospital settings, CURB-65 is preferred for its additional discriminative power. When lab results are unavailable, CRB-65 provides equivalent guidance.
Hypoxia (SpO2 <94% or <90%) is not included in CRB-65 but is a critical independent predictor of pneumonia severity. A patient with CRB-65 of 0 but SpO2 of 88% on room air needs hospital evaluation regardless. Always measure SpO2 before making a disposition decision based on CRB-65.
In the BTS validation studies, CRB-65 score 0 was associated with 30-day mortality below 1%. These patients can be safely treated with oral amoxicillin 500 mg three times daily for 5–7 days (BTS preferred first-line) in non-penicillin-allergic adults. Add a macrolide (azithromycin or clarithromycin) if atypical coverage is needed.
Even a CRB-65 score of 0 does not guarantee safe outpatient treatment if the patient cannot take oral medications, lives alone with no support, has significant frailty, or lacks access to follow-up. Social factors, functional status, and ability to recognize deterioration are clinical inputs that can override low-score reassurance.
Bilateral or multilobar pneumonia significantly increases mortality risk independently of CRB-65 or CURB-65 score. If chest X-ray shows bilateral infiltrates or two or more lobe involvement, hospitalization is generally recommended regardless of CRB-65 score, particularly in older or immunocompromised patients.
CRB-65 does not incorporate Legionella risk factors (recent travel, hotel stays, construction exposure, spa/whirlpool exposure) or MRSA risk factors (prior MRSA colonization, recent hospitalization, dialysis, skin and soft tissue infections). Severe CAP with these risk factors warrants urinary antigen testing (Legionella, pneumococcal) and potentially MRSA coverage.
Atypical CAP pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella spp.) account for 15–25% of CAP. Young, healthy patients with 'walking pneumonia' (productive cough, low-grade fever, bilateral patchy infiltrates, otherwise ambulatory) are more likely to have atypical pathogens — azithromycin or doxycycline provides appropriate coverage in outpatient low-risk CRB-65 score 0 patients.
CRB-65 and CURB-65 were validated exclusively for community-acquired pneumonia (CAP). Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) have different microbiology (gram-negative rods, MRSA, Pseudomonas) and require different severity tools such as APACHE II or the Clinical Pulmonary Infection Score (CPIS). Never use CRB-65 for HAP/VAP.
CRB-65 derived from CURB-65 (Lim et al., Thorax 2003) by removing the BUN (urea) criterion for primary care applicability. CURB-65 validated in 1068 patients across 3 UK teaching hospitals; 30-day mortality: score 0=0.7%, 1=3.2%, 2=13%, 3=17%, 4-5=57%. BTS Guidelines for Management of CAP (Lim et al., Thorax 2009) recommend both scores. IDSA/ATS 2019 Community-Acquired Pneumonia Guidelines (Metlay et al., Am J Respir Crit Care Med 2019) reference severity assessment tools for treatment intensity.
CRB-65 estimates short-term pneumonia risk using bedside variables only. Score 0 generally indicates lower risk, scores 1-2 indicate intermediate risk, and scores 3-4 indicate high risk with greater likelihood of adverse outcomes.
Use this as a structured triage aid, not as a stand-alone discharge decision.
Use CRB-65 for adults with suspected community-acquired pneumonia when laboratory testing is unavailable or delayed, especially in primary care, urgent care, tele-triage, and prehospital settings.
It helps decide whether outpatient management may be reasonable or whether urgent hospital assessment is warranted.
CRB-65 does not include oxygenation, imaging burden, lactate, comorbidity complexity, or biomarker data. Young patients with severe hypoxemia can still have deceptively low scores.
It is a triage support tool and should be interpreted with full clinical context, including respiratory status and social support.
For related assessments, see CURB-65 Score, PSI / PORT Score and NEWS2 Score.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
April 21, 2026 · trust-baseline
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