Laboratory Tests and Ancillaries
Diagnostic Tests
Sputum Analysis
Sputum analysis includes sputum smear and culture for bacteria,
mycobacteria and fungi. This reinforces the
diagnosis of bronchiectasis and provides
information regarding etiology and corresponding treatment. The isolation of Aspergillus fumigatus in sputum culture supports the diagnosis of ABPA as the underlying etiology. In patients at high risk of
non-tuberculous mycobacteria infection based on clinical and radiologic
features, a minimum of three sputum or bronchoalveolar lavage samples should be
tested. The sputum is also frequently positive for Haemophilus influenzae, P aeruginosa, and Streptococcus pneumoniae.
Pulmonary Function Tests
Pulmonary function
tests are useful in obtaining a functional assessment of the patient and may
reflect underlying diseases. It must be noted that the most common abnormality observed
is an obstructive and restrictive airway defect, especially in patients with
more severe diseases. Lastly, pulmonary function tests may be normal in
localized and mild bronchiectasis.
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Routine Laboratory
Tests
Laboratory tests
that can be done include complete blood count, serum electrophoresis, serum
immunoglobulins (Ig) (total IgG, IgA, IgM), total IgE, and Aspergillus-specific
IgE and IgG.
Other Tests 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 and to test for non-tuberculous
mycobacteria-related diseases.
The following diagnostic tests may be done in the appropriate clinical setting:
- Pilocarpine iontophoresis (sweat test) for CF transmembrane conductance regulator genetic testing 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
- Antibody titers for S pneumoniae
- 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 (bronchial dilatation) 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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