Investigation of difficult/therapy-resistant asthma
| Assessment of severity |
| Symptom score chart and use of β2-agonist reliever therapy |
| Spirometric measurement of lung volumes and gas transfer |
| Bronchial responsiveness to methacholine/histamine |
| Diurnal variation in peak expiratory flow |
| Quality of life assessment |
| Determination of pharmacological responsiveness |
| Assessment of compliance to therapy and inhaler technique |
| Bronchodilator response to β2-adrenergic agonists |
| Response to prednisolone (corticosteroid responsiveness) |
| Radiology |
| Chest radiograph |
| Barium swallow |
| Computed tomography of sinuses |
| High-resolution computed tomography of the lungs |
| Blood tests |
| Full blood count, including eosinophil count |
| Serum IgG, IgA, IgM and IgG subclasses |
| Serum total IgE |
| Specific IgE to selected allergens |
| Thyroid function tests |
| Other tests |
| Biomarkers of inflammation (exhaled nitric oxide, eosinophils in induced sputum) |
| Sweat test and genetic assessment of CFTR mutations (if indicated) |
| 24-h oesophageal pH monitoring |
| Examination of nasopharyngeal airways |
| Tests of ciliary function |
| Skin-prick test to common aeroallergens |
| Fibreoptic bronchoscopy with bronchial biopsy and bronchoalveolar lavage |
| Psychological assessment |
Ig: immunoglobulin; CFTR: cystic fibrosis transmembrane conductance regulator. Reproduced from [8] with permission from the publisher.