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

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 ³.
• 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 ².
• Perform a physical examination to identify expiratory polyphonic wheeze, although a normal exam does not exclude asthma ³.
• 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 ²,³.
• 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 ¹,³.
• 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 ¹,².
• If diagnosis remains uncertain or cough does not respond to treatment trials, refer to a respiratory specialist for further assessment ¹.