Investigations to be considered in a young person with difficult-to-treat asthma

InvestigationSpecification and description
Asthma control and quality of life quantificationACQ, AQLQ, HADS
Allergy testsSpecific IgE, total IgE, aeroallergen- and food-specific IgE, skin prick testing (guided by history)
Type 2 asthma biomarkersFENO, blood eosinophils, sputum eosinophils
Screening for other diseases including metabolic screenConnective disease screen, vasculitis, immunoglobulins, functional antibodies#, vitamin D, cortisol assay, HbA1c, lipid profile
Lung functionFull set, loops, gas transfer, reversibility, peak flow records, bronchial provocation testing
RadiologyChest 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 nasendoscopyCPET for unexplained breathlessness and BPD
Nasendoscopy for suspected ILO
BronchoscopyUpper 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.