Table 4 Potentially serious lung disorders with chronic coughing
Cystic fibrosisSweat test, nasal potential difference, assessment of pancreatic function, genotyping
Immune deficienciesDifferential white cell counts, immunoglobulin levels and subsets, functional antibody responses and lymphocyte subset analysis
Primary ciliary disordersScreening FnNO, saccharine test, cilial ultrastructure and function, culture of ciliated epithelium
Protracted bacterial bronchitisChest radiography, sputum for culture, exclusion of other causes in this table. Response to 4–6 weeks antibiotic and physiotherapy
HRCT scan
Recurrent pulmonary aspiration:    Laryngeal cleft or ‘H’ type tracheo-oesophageal fistula    Post-TOF repair with swallowing incoordination    Neuromuscular or neurodevelopmental disorder    GOR, hiatal herniaBarium swallow, videofluoroscopy, 24 h pH studies, milk isotope scan, fat-laden macrophage index* on bronchalveolar lavage if bronchoscopy indicated. Oesophagoscopy with biopsy may be indicated.
NB. There is little evidence that GOR alone is a cause of cough in otherwise healthy children
Retained inhaled foreign bodyChest radiography and HRCT scan may show focal lung disease
Rigid bronchoscopy is both diagnostic and therapeutic and is almost always indicated if the history is suggestive of inhaled retained foreign body
TuberculosisChest radiography, Mantoux, early morning gastric aspirates and gamma interferon tests
Anatomical disorder (eg, bronchomalacia) or lung malformation (eg, cystic congenital thoracic malformation)Bronchoscopy and CT scan
Interstitial lung diseaseSpirometry (restrictive defect), chest radiography and HRCT scan, lung biopsy
  • FnNO, fractional nasal nitric oxide; HRCT, high-resolution CT; TOF, tracheo-oesophageal fistula; GOR, gastro-oesophageal reflux.

  • *Fat-laden macrophages in bronchoalveolar lavage fluid may not be a specific test for recurrent pulmonary aspiration.

  • Most should have a chest radiograph and an attempt to obtain sputum for microbiology. A high-resolution CT scan may be indicated to determine the extent of disease, eg focal versus generalised.