Diagnostic tests play a key role in uncovering underlying etiologies of chronic cough, such as chronic obstructive pulmonary disease (COPD), gastroesophageal reflux disease (GERD), or use of angiotensin-converting enzyme (ACE) inhibitors [18–20], but recent studies have found that even after thorough investigation and treatment, 20% to 40% of chronic cases do not respond to guideline-based treatment [21, 22]. This evidence concerns the gene ACE and chronic obstructive pulmonary disease.