What initial investigations should I consider for a patient with a chronic cough lasting more than eight weeks?

For a patient presenting with a chronic cough lasting more than eight weeks, initial investigations in General Practice should consider:

• Chest X-ray: This should be offered urgently (within 2 weeks) for unexplained cough in patients aged 40 and over who have ever smoked or been exposed to asbestos ⁴. It should also be considered urgently for persistent or recurrent chest infections in patients aged 40 and over ⁴.
• Spirometry: This is crucial for diagnosing Chronic Obstructive Pulmonary Disease (COPD), especially in people over 35 with a history of smoking or other risk factors ³. Post-bronchodilator spirometry is used to confirm a COPD diagnosis ³.
• Serial home peak flow measurements: These can be used to help exclude asthma if there is diagnostic uncertainty ³.

Additionally, an important initial consideration is to assess for an Angiotensin-converting enzyme (ACE) inhibitor-induced cough. If suspected, stopping the ACE inhibitor treatment and prescribing an alternative is an initial management step, with the cough typically resolving within one month ¹.

If the cough does not respond to initial therapeutic trials, or the diagnosis remains uncertain, referral to a respiratory physician for specialist assessment and further investigations (such as methacholine challenge, sputum cytology, or immunologic tests) may be necessary ¹. In palliative care, investigations like a chest X-ray may be considered if a pleural effusion is suspected, with more advanced imaging (CT/MRI) or bronchoscopy potentially carried out in secondary care ².