Cause | Investigation |
Aspiration (silent) | Video fluoroscopy |
Gastro-oesophageal reflux disease | pH/impedance study with or without milk scan |
Bronchiectasis | High-resolution chest CT with or without contrast |
Immunodeficiency | Immunoglobulins and vaccine responses |
Cystic fibrosis | Sweat test and genetic analysis |
Primary ciliary dyskinesia | Nasal nitric oxide ± ciliary brushings |
Congenital heart disease | Echocardiogram |