Investigation
Pulse oximetry and blood gas analysis (ABG)
Blood gas analysis should be performed if oxygen saturation (SpO2) is < 94%.
In allergic asthma
- Total IgE, allergen-specific IgE
- CBC: possibly Eosinophilia
- AEC > 400
Pulmonary function testing (spirometry)
- First-line diagnostic test for confirmation of the diagnosis in patients ≥ 5 years of age. Asthma is diagnosed by demonstration of reversible airway obstruction in spirometry
Methacholine challenge test(Bronchoprovocation test):
- Evidence of bronchial hyper responsiveness after inhalation of methacholine
Chest X-Ray
- To exclude differential diagnoses (e.g. pneumonia, pneumothorax)
- Normal in mild cases
- Signs of pulmonary hyperinflation in cases of severe asthma
- Low, flattened diaphragm
- Wide inter costal spaces
- Barrel chest
Skin allergy tests:
- Skin prick testing (SPT) or intra dermal skin testing
- In asthma triggered by infection: elevated inflammatory markers
Sputum sample
- Curschmann spirals (whorled mucous plug in sputum that is formed by shed bronchial epithelium)
- Charcot-Leyden crystals (histopathologic finding in patients with eosinophilic inflammation and/or proliferation)
- Creola bodies (aggregate of desquamated epithelial cells)