What investigations are used to diagnose and manage bronchiectasis?

Investigations in Bronchiectasis

Diagnostic Imaging

Perform a baseline chest X-ray followed by thin-section CT scan to confirm the diagnosis of bronchiectasis when clinically suspected. 1

Initial Imaging Approach

• Obtain a baseline chest X-ray in all patients with suspected bronchiectasis, though sensitivity is only 87.8% and specificity 74.4% compared to HRCT 1
• Perform thin-section CT scan to definitively confirm bronchiectasis diagnosis, as this is the gold standard with false positive and negative rates of only 1% and 2% respectively 1
• Conduct imaging during clinically stable disease for optimal diagnostic accuracy and to establish a baseline for serial comparisons 1

CT Technical Specifications

• Use volumetric CT with high-resolution technique rather than conventional HRCT alone, as it demonstrates improved sensitivity and interobserver agreement 1
• Apply dose reduction techniques including adaptive mA and kV with iterative reconstruction when available 1
• In children and adolescents, use a bronchoarterial ratio (BAR) threshold >0.8 rather than the adult cut-off of >1.0, as pediatric airways have lower normal BAR values 1

CT Diagnostic Criteria

Bronchiectasis is confirmed by one or more of the following findings 1:

• Bronchoarterial ratio >1 (internal airway lumen diameter compared to adjacent pulmonary artery)
• Lack of bronchial tapering as airways extend peripherally
• Airway visibility within 1 cm of costal pleural surface or touching mediastinal pleura

Associated indirect signs include 1:

• Bronchial wall thickening
• Mucus impaction
• Mosaic perfusion/air trapping on expiratory CT

Clinical Indications for Investigation

Primary Indications

Investigate for bronchiectasis in patients with persistent mucopurulent or purulent sputum production, particularly with relevant risk factors. 1, 2, 3

• Chronic productive cough is the cardinal feature warranting investigation 3
• Cough persisting longer than 8 weeks with sputum production should trigger diagnostic workup 1, 2, 3
• Recurrent chest infections in at-risk populations require evaluation 3

High-Risk Populations Requiring Lower Threshold for Investigation

• Rheumatoid arthritis patients with chronic productive cough or recurrent chest infections, as bronchiectasis may precede RA diagnosis in 58% of cases 1, 2
• COPD patients with ≥2 exacerbations annually and positive sputum culture for P. aeruginosa while stable 1, 2
• Inflammatory bowel disease patients with chronic productive cough 1, 2
• Severe or poorly-controlled asthma patients 1, 2
• Immunosuppressed patients including those with HIV, solid organ/bone marrow transplant recipients, and those on immunosuppressive therapy 1, 2
• Chronic rhinosinusitis patients with chronic productive cough or recurrent infections 1

Etiological Investigations

Minimum Panel of Tests (Adults)

Once bronchiectasis is confirmed radiographically, investigate the underlying cause with 1:

• Sputum culture for microbiology including bacterial pathogens and consideration for nontuberculous mycobacteria
• Full blood count to assess for inflammatory markers
• Immunoglobulin levels (total IgG, IgA, IgM, IgE) and specific antibodies to vaccine antigens
• Sweat chloride test to exclude cystic fibrosis in appropriate clinical contexts
• Spirometry to assess baseline lung function

Minimum Panel for Children and Adolescents

In pediatric patients with confirmed bronchiectasis, perform a comprehensive minimum panel including: 1

1. Chest CT scan (for diagnosis)
2. Sweat test
3. Lung function tests (in those who can perform spirometry)
4. Full blood count
5. Immunological tests (total IgG, IgA, IgM, IgE and specific antibodies to vaccine antigens)
6. Lower airway bacteriology

Additional Investigations Based on Clinical Presentation

Consider targeted additional testing when clinical features suggest specific etiologies: 1

• In-depth immunological assessment in consultation with an immunologist if initial screening suggests immunodeficiency (diagnostic yield 42%) 1
• Diagnostic bronchoscopy with bronchoalveolar lavage for microbiology when sputum cannot be obtained or for specific diagnostic questions (diagnostic yield 12-41%) 1
• Primary ciliary dyskinesia testing (nasal nitric oxide, ciliary biopsy, genetic testing) when distribution pattern or clinical history suggests this diagnosis 1
• Alpha-1 antitrypsin levels in patients with lower lobe predominant disease or early-onset emphysema 1
• ABPA testing (specific IgE to Aspergillus, total IgE, eosinophil count) when upper lobe predominant disease with mucus plugging is present 1
• Tuberculosis assessment in endemic areas or with relevant exposure history 1
• HIV testing in high-prevalence settings or with risk factors 1
• Gastroesophageal reflux and aspiration testing when clinical history suggests these conditions 1

Critical Pitfalls to Avoid

• Do not rely on physical examination alone to diagnose or exclude bronchiectasis, as crackles and rhonchi are nonspecific and examination can be normal even with confirmed disease 2, 3
• Do not use BAR alone to diagnose bronchiectasis; combine radiographic findings with consistent clinical features 1
• Do not perform CT during acute exacerbations as inflammatory changes may overestimate disease extent 1
• Recognize that 34% of patients have no identifiable cause despite comprehensive testing, so absence of identified etiology does not exclude the diagnosis 1

Role of CT in Identifying Etiology

CT patterns can suggest specific underlying causes: 1

• Upper lobe predominance with mucus plugging suggests ABPA
• Central bronchiectasis suggests ABPA or post-tuberculous disease
• Diffuse disease with situs abnormalities suggests primary ciliary dyskinesia
• Lower lobe predominance may suggest aspiration or alpha-1 antitrypsin deficiency
• Tree-in-bud nodularity suggests active infection including nontuberculous mycobacteria