22nd February 2024

Diagnosis

Bronchiectasis should be suspected in individuals with recurrent purulent or mucopurulent sputum. Diagnosis is confirmed using results from laboratory tests, pulmonary function assessment and radiographic evidence. 

Investigations

• Raised inflammatory markers such as White Blood Cell (WBC) counts, in particular neutrophil count and c-reactive protein, are commonly associated with exacerbations of bronchiectasis. 
• Reduction in immunoglobulin profiles, such as IgG, IgM and IgA, are associated with bronchiectasis. Specific gene testing, such as the CFTR gene for cystic fibrosis, can also be linked with bronchiectasis. 
• Sputum culture: Pseudomonas colonisation is commonly associated with bronchiectasis exacerbation, requiring a longer duration of intravenous and oral antibiotics
• Rheumatoid factor: Bronchiectasis can be a feature of rheumatoid arthritis and is often associated with severe nodular disease.  
• Alpha 1 antitrypsin: A deficiency of alpha 1 antitrypsin is pathognomonic for COPD and helps differentiate bronchiectasis from COPD.

Pulmonary function tests

Spirometry is likely to show an obstructive pattern due to damage to the lung parenchyma from bronchiole dilatation and impairment of the mucociliary escalator, thereby causing a reduction of oxygen transfer and retention of carbon dioxide within the pulmonary capillary system. The patient will also have decreased Forced Expiratory Volume (FEV 1) as compared to Forced vital capacity (FVC), thus overall ratio of FEV1 / FEV <70 %.

Radiological evidence

Chest radiograph 

Most patients with bronchiectasis will have an abnormal chest radiograph. Although not diagnostic, common features include patchy lower zone opacification, linear atelectasis, and dilated and thickened airways (appearance of ‘tram lines’ / ring shadows).

Computed tomography (CT) 

High-resolution computed tomography (HRCT) is the gold standard imaging modality for confirming the diagnosis of bronchiectasis. Features of HRCT include:

• Airway dilatation can appear as a parallel / ‘tram line’ on chest X-ray. Dilated airways with accompanying pulmonary vessels can appear as  ‘signet rings’ on HRCT. Airway lumen dilatation of >1.5mm to adjacent pulmonary vessels is the classic diagnostic feature of bronchiectasis. 
• Smaller airways can present in a linear fashion, giving the appearance of a ‘tree in bud’ pattern on HRCT. 
• The distribution seen on HRCT  may be associated with different aetiologies of bronchiectasis:
  • The central (perihilar) pattern is more suggestive of allergic bronchopulmonary aspergillosis
  • Upper lobe distribution is significant for cystic fibrosis
  • Middle/lower lobe correlates with primary ciliary dyskinesis 
  • Lingula segment of the upper left lung with non-tuberculosis mycobacterium (NTM). 
• Airway visibility of 1cm around coastal pleural space or touching mediastinal pleura. 

References

• Hill AT, Sullivan AL, Chalmers JD, et al. British Thoracic Society Guideline for bronchiectasis in adults. Thorax 2019; 74:1.
• Riordan JR. Assembly or functional CFTR chloride channels. Annu Rev Physiol. 2005;67:701–718. 
• LeGrys VA, Yankaskas JR, Quittell LM, et al. Diagnostic sweat testing: the Cystic Fibrosis Foundation guidelines. J Pediatr 2007; 151:85.
• Aliberti S, Goeminne PC, O’Donnell AE, et al. Criteria and definitions for the radiological and clinical diagnosis of bronchiectasis in adults for use in clinical trials: international consensus recommendations. Lancet Respir Med 2022; 10:298