Laboratory Tests and Ancillaries
Diagnostic Tests
Sputum Analysis
Sputum analysis includes sputum culture and smear for bacteria, mycobacteria and fungi. This reinforces the diagnosis of bronchiectasis and adds significance to the information regarding the etiologies and treatment. The isolation of Aspergillus fumigatus in sputum culture supports the diagnosis of ABPA as the underlying etiology. The sputum is also frequently positive for Haemophilus influenzae, P aeruginosa, and Streptococcus pneumoniae.
Pulmonary Function Tests
Pulmonary function tests may reflect underlying diseases. It may be normal in localized and mild bronchiectasis. It must be noted that the most common abnormality is an obstructive and restrictive airway defect, especially in patients with more severe disease. Lastly, pulmonary function tests are useful in obtaining a functional assessment of the patient.
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Laboratory Tests
Laboratory tests that can be done include complete blood count, serum immunoglobulins (Ig) (total IgG, IgA, IgM), and antibody titers for S pneumoniae. IgE and IgG antibodies are specific for Aspergillus.
Other Diagnostic Studies to Confirm Underlying Etiologies
Results of other diagnostic studies may assist in the management and prognosis of the patient. For example, flexible bronchoscopy can be done to rule out obstruction by foreign bodies.
The following diagnostic tests may be done in the appropriate clinical setting:
- Pilocarpine iontophoresis (sweat test) for CF
- Autoimmune serology
- Rheumatoid factor and anti-cyclic citrullinated peptide antibodies for rheumatoid disease
- Aspergillus precipitins/IgG, IgE in blood and skin test for ABPA
- A1AT levels if there is evidence of chronic obstructive pulmonary disease or emphysema
- Vitamin D levels if deficiency is suspected
- Genetic testing for primary ciliary dyskinesia and CF
- Human immunodeficiency virus (HIV) or T-lymphotrophic virus type 1 testing if clinically suspected
- Echocardiogram in adults if there is suspicion of secondary pulmonary hypertension
- Lung function testing (eg body plethysmography, gas transfers, measures of small airway function, and walk test)
Imaging
Baseline imaging is performed during clinically stable disease for diagnosis and serial comparison.
Chest X-ray
The following chest X-ray findings are suspicious but non-diagnostic in bronchiectasis patients, linear atelectasis, dilated and thickened airways (tram or parallel lines; ring shadows on cross section), and irregular opacities representing mucopurulent plugs. Chest X-ray may also be done to evaluate for pneumonia if the patient complains of fever, chills, night sweats or difficulty of breathing during consultation.
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High-Resolution CT (HRCT) Scan
HRCT is a defining test for bronchiectasis with high sensitivity and specificity. It assesses the severity of the disease by measuring the number of bronchopulmonary segments affected or the percentage of the lobes involved.
Indications for HRCT include the following:
- There are suspicious clinical findings but a relatively normal chest radiograph
- Abnormal chest radiograph and bronchiectasis is suspected
- Management decisions must be made depending on the extent of bronchiectasis
- Presence of confounding diseases needs to be defined
Findings in HRCT include diagnostic features such as lack of normal tapering of bronchi (tram track appearance), bronchial diameter is larger than the accompanying pulmonary artery (signet ring sign), and peripheral airways are seen within 1 cm of the costal pleura. Other non-specific findings in HRCT for bronchiectasis include bronchial wall thickening, dilated airways with air-fluid levels, mucopurulent plugs or debris accompanied by post-obstructive air trapping, “tree-in-bud” pattern when small airways are affected, more destructive bronchiectasis shows cysts on the bronchial wall, and consolidation of a segment or lobe may also be seen.
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