Tests to distinguish severe asthma from alternative diagnosis that may mimic asthma
| Routine screening test in adults | Exclusion (if test is normal) |
| Air trapping measured by body plethysmography | Bronchiolitis obliterans |
| Carbon monoxide diffusion capacity | Emphysema or parenchymal lung disease |
| Chest HRCT scan | Parenchymal lung disease |
| Bronchiolitis obliterans | |
| Bronchiectasis | |
| Congestive heart failure | |
| D-dimer | Recurrent pulmonary embolism |
| Suspected alternative or additional diagnoses in adults | Diagnostic test |
| Intrabronchial obstruction | Bronchoscopy |
| Vocal cord dysfunction | Laryngoscopy during attack |
| Dysfunctional breathing/panic attacks | Blood gases during attack |
| Hyperventilation provocation test | |
| Recurrent microaspiration | Proximal oesophageal pH measurement |
| Bile salts in bronchoalveolar lavage fluid | |
| Cystic fibrosis (CF) | Sweat test |
| Allergic bronchopulmonary aspergillosis (ABPA) | Aspergillus IgE/precipitins/sputum culture |
| Emphysema | High resolution CT scan |
| Hypersensitivity pneumonitis | |
| Bronchiectasis (including ABPA, CF) | |
| Recurrent pulmonary embolism | CT pulmonary angiography |
| Pulmonay arterial hypertension | |
| Bronchiolitis | Transbronchial or thoracoscopic lung biopsy |
| Sarcoidosis | |
| Systemic | |
| Churg–Strauss syndrome | Biopsy of affected organ(s) |
| Antineutrophilic cytoplasmic antibodies |
| Suspected alternative or additional diagnoses in children | Diagnostic test |
| Structural abnormalities (tracheobronchial malacia, vascular compression/rings, tracheal stenosis/webs, cystic lesions/masses, tumours/lymphadenopathy/cardiomegaly) | Fibreoptic bronchoscopy |
| Thorax CT scan | |
| Intrabronchial obstruction (eg, inhaled foreign body) | Rigid bronchoscopy |
| Vocal cord dysfunction | History, direct observation |
| Dysfunctional breathing/panic attacks | History, direct observation |
| Gastro-oesophageal reflux with/without recurrent microaspiration | Proximal oesophageal pH measurement |
| Bile salts in bronchoalveolar lavage fluid | |
| Cystic fibrosis (CF) | Sweat test |
| Immune abnormalities | Serum immunoglobulins including IgA, G, M and IgG subclasses and vaccine antibody responses (Haemophilus, tetanus and Pneumococcus) |
| Bronchiectasis (including CF, primary ciliary dyskinesia) | High resolution CT scan |
| Bronchopulmonary dysplasia | History of prematurity |
| Bronchiolitis obliterans | High resolution CT scan |
| Lung biopsy |