Investigations to be considered in a young person with difficult-to-treat asthma
| Investigation | Specification and description |
| Asthma control and quality of life quantification | ACQ, AQLQ, HADS |
| Allergy tests | Specific IgE, total IgE, aeroallergen- and food-specific IgE, skin prick testing (guided by history) |
| Type 2 asthma biomarkers | FENO, blood eosinophils, sputum eosinophils |
| Screening for other diseases including metabolic screen | Connective disease screen, vasculitis, immunoglobulins, functional antibodies#, vitamin D, cortisol assay, HbA1c, lipid profile |
| Lung function | Full set, loops, gas transfer, reversibility, peak flow records, bronchial provocation testing |
| Radiology | Chest radiography, bone density scan CT-scan of thorax (dynamic inspiratory and expiratory and lung parenchyma high-resolution scan) in cases of diagnostic uncertainty and suspicion of EDAC or TBM |
| CPET and nasendoscopy | CPET for unexplained breathlessness and BPD Nasendoscopy for suspected ILO |
| Bronchoscopy | Upper airway, TBM and EDAC, airway disease, BAL, biopsies |
ACQ: Asthma Control Questionnaire; AQLQ: Asthma Quality Of Life Questionnaire; HADS: Hospital Anxiety and Depression Score; FENO: fraction exhaled nitric oxide; HbA1c: haemoglobin A1C; CT: computed tomography; EDAC: excessive dynamic airway collapse; TBM: tracheobronchomalacia; CPET: cardiopulmonary exercise test; BAL: bronchoalveolar lavage; BPD: breathing pattern disorder; ILO: inducible laryngeal obstruction. #: Functional antibodies refer to serum IgG antibodies to Streptococcus pneumoniae (pneumococcus) and Haemophilus influenzae.