Investigations for secondary causes

Spirometry (FEV₁, FVC, PEF) and TLCO

to document baseline lung function

for the measurement and monitoring of severity of disease

presence of bronchodilator response (reversibility)

Sputum sample (microbiology and culture)

identify the presence of bacteria or organisms in the sputum

include mycobacterial culture

persistent Staphylococcus aureus may indicate ABPA or CF

surveillance of sputum microbiology helps guide antibiotic therapy

Pathology

full blood count and differential white cell count – Neutropenia/lymphopenia/lymphocytosismay suggest immune deficiency. Eosinophilia suggests asthma or ABPAimmunodeficiency screening – IgG, IgA, IgM and IgG subclass levels (derived from a venous blood sample). Low immunoglobulins suggest a primary (eg CVID) or secondary immunodeficiency state (see Management Strategies for more information on immunotherapy)serum total IgE, aspergillus precipitins – IgE less than 1000IU/mL and positive aspergillus precipitins is consisitent with ABPAconnective tissue and vasculitis screening – rheumatoid factor, anti-CCP antibodies, antinuclear antibodies, antineutrophil cytoplasmic antibodiesidentifying ABPA – Aspergillus in sputum, total IgE, Aspergillus RAST, Aspergillus precipitins (IgG)

Vaccine responses:

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Bronchoscopy indicated when:

response to treatment is poor

HRCT indicative of mycobacterial infection

disease is localised (to exclude obstruction)

unexplained haemoptysis

Exhaled nasal nitric oxide

indicated if considering primary ciliary dyskinesia. This should be considered in cases of dextrocardia, chronic childhood sinusitis or upper respiratory tract infections

studies of ciliary structure and function should be considered in adults with a history of chronic upper respiratory tract infections or otitis media

Sweat test

to exclude cystic fibrosis – CF needs to be excluded in all patients presenting at < 40 years of age and those > 40 years of age where no other cause is evident and there is persistent isolation of Staphylococcus aureus in the sputum, features of malabsorption, male primary infertility or upper lobe bronchiectasis