How can I differentiate between asthma and chronic cough due to other

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

To differentiate asthma from chronic cough caused by other underlying conditions in primary care:

Take a detailed clinical history focusing on symptoms typical of asthma such as wheeze, breathlessness, chest tightness, cough with diurnal or seasonal variation, and triggers that worsen symptoms. Also check for a personal or family history of asthma or allergic rhinitis .
Look for asthma-specific features like night-time waking with breathlessness or wheeze and significant day-to-day variability of symptoms, which are common in asthma but uncommon in other causes like COPD .
Perform a physical examination to identify expiratory polyphonic wheeze, although a normal exam does not exclude asthma .
Use objective tests to support diagnosis: spirometry with reversibility testing can help, but routine reversibility testing is not always necessary; serial peak flow measurements may help exclude asthma if diagnostic doubt remains ,.
Consider a trial of inhaled corticosteroids (ICS) for 2–4 weeks to assess response, as asthma and eosinophilic bronchitis typically improve with ICS, whereas other causes may not ,.
Rule out other common causes of chronic cough such as ACE inhibitor use, gastro-oesophageal reflux disease, upper airway cough syndrome (post-nasal drip), smoking-related cough, bronchiectasis, COPD, and environmental or occupational exposures by history, examination, and appropriate investigations ,.
If diagnosis remains uncertain or cough does not respond to treatment trials, refer to a respiratory specialist for further assessment .

How can I differentiate between asthma and chronic cough due to other causes in a primary care setting?