Cough in Adults

Differential Diagnosis

Common Diagnoses

Rare Diagnoses

  • TB
  • Other Medication Side Effect (e.g. Methotrexate)
  • Pulmonary Fibrosis
  • Fibrosing Alveolitis
  • Extrinsic Allergic Alveolitis
  • Psychogenic
  • Cough in Adults
  • Inhaled Foreign Body
  • Diaphragmatic Irritation (e.g. Abscess)

Ready Reckoner

Key distinguishing features of the most common diagnoses

URTILRTI AsthmaCOPDACE Inhibitor Side Effect
Associated Shortness of Breath NoPossiblePossibleYes No
Productive CoughPossibleYesPossibleYes No
Persistent or Recurrent Cough No NoYesYesYes
Audible Wheeze NoPossiblePossiblePossible No
On ACE InhibitorPossiblePossiblePossiblePossibleYes

Possible Investigations


Possible:FBC, ESR/CRP, spirometry, PEFR.

Small Print:Sputum, cardiac investigations, serum precipitins, hospital-based investigations such as CT scan and bronchoscopy.

  • FBC: Hb may be reduced in malignancy and chronic illness; WCC raised in infections, eosinophils raised in allergic conditions.
  • ESR/CRP: Raised in neoplasia, infective and inflammatory conditions.
  • CXR: May show signs in a variety of the relevant differentials, such as LRTI, tumour and TB.
  • Spirometry: May show characteristic patterns particularly in asthma, COPD and pulmonary fibrosis.
  • Serial peak flow: May be helpful in diagnosis of asthma (guidance recommends testing fractional exhaled nitric oxide in suspected asthma but this may not be practical, or available).
  • Sputum: May be useful in diagnosing TB and occasionally helps guide antibiotic treatment in LRTI or exacerbation of COPD.
  • Cardiac investigations: Such as BNP or echocardiogram if LVF suspected.
  • Serum precipitins: In suspected extrinsic allergic alveolitis.
  • Hospital-based investigations: Further investigations such as CT scan or bronchoscopy may be required to clarify CXR abnormalities or pursue clinical suspicion.

Top Tips

  • Explain to patients that it is not unusual for the cough of a simple URTI to go on for 3 weeks – this will reduce unnecessary re-attendances.
  • Take a careful history of provoking factors in the case of persistent cough – this is more likely to reveal the diagnosis than is chest auscultation.
  • Have a low threshold for arranging a CXR in the middle-aged and elderly smoker with a cough.
  • ACE inhibitor-associated cough may come on many months – or even longer – after initiating treatment. It starts to improve within 1–4 weeks of stopping treatment but may take 3 months to settle completely.
  • In a persistent cough with a normal CXR and no chest signs, think asthma, GORD and rhinitis – a therapeutic trial for each may be needed to clinch the diagnosis.

Red Flags

  • Remember to ask about foreign travel. Atypical pneumonias are infrequent, and TB rare, but both can still present.
  • Beware of persistent cough, weight loss and voice change in a smoker – arrange an X-ray to exclude malignancy.
  • Night sweats with persistent cough suggest significant pathology such as TB or malignancy.
  • Beware the patient on immunosuppressants – these drugs may alter the clinical picture, predispose to serious complications and in some cases (e.g. methotrexate) may be the cause of the cough itself.
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