How is the Bronchiectasis Severity Index (BSI) calculated at diagnosis to stratify risk of future complications?

Calculating the Bronchiectasis Severity Index (BSI) at Diagnosis

The BSI should be calculated at diagnosis using nine clinical variables that are readily available: age, BMI, FEV1% predicted, prior hospitalization, exacerbation frequency, MRC dyspnea score, Pseudomonas aeruginosa colonization, other organism colonization, and radiological extent—with total scores of 0-4 indicating mild disease, 5-8 moderate disease, and ≥9 severe disease. 1

How to Calculate the BSI

The BSI combines the following variables with specific point allocations 1:

Age Points

• <50 years: 0 points
• 50-69 years: 2 points
• 70-79 years: 4 points
• ≥80 years: 6 points

BMI (kg/m²) Points

• <18.5: 2 points
• 18.5-25: 0 points
• 26-30: 0 points

• 30: 0 points

FEV1% Predicted Points

• 80%: 0 points

• 50-80%: 1 point
• 30-49%: 2 points
• <30%: 3 points

Hospital Admission (within last 2 years)

• No: 0 points
• Yes: 5 points

Exacerbations (previous 12 months)

• 0: 0 points
• 1-2: 0 points
• ≥3: 2 points

MRC Breathlessness Score

• 1-3: 0 points
• 4: 2 points
• 5: 3 points

P. aeruginosa Colonization

• No: 0 points
• Yes: 3 points

Colonization with Other Organisms

• No: 0 points
• Yes: 1 point

Radiological Severity

• <3 lobes affected: 0 points
• ≥3 lobes or cystic bronchiectasis in any lobe: 1 point

Risk Stratification and Prognostic Implications

The BSI was specifically designed to predict future exacerbations, hospitalizations, health status, and mortality over 4 years 1. The score demonstrates excellent discriminatory ability with validated outcomes across multiple European cohorts 2, 3.

Mild Disease (0-4 points)

• 1-year mortality: 0-2.8%
• 1-year hospitalization: 0-3.4%
• 4-year mortality: 0-5.3%
• 4-year hospitalization: 0-9.2% 1

Moderate Disease (5-8 points)

• 1-year mortality: 0.8-4.8%
• 1-year hospitalization: 1.0-7.2%
• 4-year mortality: 4-11.3%
• 4-year hospitalization: 9.9-19.4% 1

Severe Disease (≥9 points)

• 1-year mortality: 7.6-10.5%
• 1-year hospitalization: 16.7-52.6%
• 4-year mortality: 9.9-29.2%
• 4-year hospitalization: 41.2-80.4% 1

Clinical Implementation

An online calculator is available at www.bronchiectasisseverity.com to facilitate rapid calculation 1. The 2025 European Respiratory Society guidelines now strongly recommend that all newly diagnosed patients with bronchiectasis should have a BSI calculated to assess risk of future complications 4.

Key Advantages of BSI Over FACED

The BSI consistently outperforms the FACED score in predicting clinically relevant outcomes 3. While both scores predict mortality adequately (pooled AUC 0.76 for both), the BSI demonstrates superior sensitivity (65% vs 28%) for mortality prediction and significantly better performance for hospitalization prediction (pooled AUC 0.82 vs 0.65) 3. The BSI also accurately predicts exacerbations, quality of life, respiratory symptoms, 6-minute walk distance, and lung function decline, whereas FACED shows poor discrimination for these outcomes 3.

Important Clinical Caveats

• The BSI was validated in patients without nontuberculous mycobacterial (NTM) infection, so interpretation should be cautious in this population 1
• It is not known whether changes in BSI score over time reflect changes in prognosis—the score is best used as a baseline assessment tool 1
• In Aboriginal Australian populations, the BSI may require adjustment (using relative scores when data is missing), as standard cutoffs may not perform optimally 5
• Patients at higher risk should be identified for more frequent follow-up and lower treatment thresholds, including those with COPD, PCD, or RA-associated bronchiectasis, P. aeruginosa colonization, ≥2 exacerbations per year, or severe symptoms 4