Table 1

Basic investigations for the aetiology of bronchiectasis

Investigations	Rationale
Sweat test/cystic fibrosis genetics	Exclude cystic fibrosis, diagnose non-classical cystic fibrosis
Immune function
White cell count	White cell differential
Total immunoglobulins	Hypogammaglobulinaemias
Antibody responses to vaccination, eg, tetanus, pneumococcus and Haemophilus influenzae B	Functional antibody problems
±Mannose binding lectin, C3 and C4	Part of complement pathways
24 h pH study/impedence study
Barium meal	Gastro-oesophageal reflux
Videofluoroscopy	Aspiration
Flexible bronchoscopy	Foreign body, malacia, abnormal anatomy
Bronchoalveolar lavage	Microbiological investigations Fat laden macrophages – aspiration
Nasal nitric oxide±ciliary biopsy	Primary ciliary dyskinesia