Table 3.

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 sinuses

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

^* Notes: Ig – immunoglobulin

^**CFTR – cystic fibrosis transmembrane conductance regulator