Cough Classification and Prevalence

Study Notes

Cough is the body's natural reflex to clear the airways of foreign matter.
Cough is a common symptom and often indicates a respiratory issue
Cough can be debilitating and disruptive to daily life.
Cough is classified as productive (chesty) or nonproductive (dry).
The British Thoracic Society Guidelines (2019) suggest most coughs resolve within 3-4 weeks without antibiotics.

Cough duration determines classification:
- Acute: less than 3 weeks
- Subacute: 3 to 8 weeks
- Chronic: more than 8 weeks
Patients with cough exceeding 3 weeks should be referred to a medical practitioner for further investigation.

Most acute coughs (20% of consultations) are caused by viral upper respiratory tract infections (URTIs).
Schoolchildren experience more coughs than adults, with an estimated 7 to 10 episodes annually compared to 2 to 5 episodes in adults.
Viral URTIs tend to increase during winter months.

Viruses cause the majority (90%) of URTIs including respiratory syncytial virus, rhinovirus and influenza.
Bacteria are responsible for the remaining 10% of infections, including Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus and Klebsiella pneumoniae.
A complex five-part cough reflex triggers the cough response.

Viral infection is the most likely cause of acute cough in primary care for all age groups.
Recurrent viral bronchitis is prevalent in preschool and young school-aged children, being the main cause of persistent cough in this age group.
While viral infections are the most probable cause, other conditions should be considered:
- Likely: Upper airways cough syndrome (postnasal drip), acute bronchitis
- Unlikely: Croup, chronic bronchitis, COPD, asthma, pneumonia, ACE inhibitor induced
- Very unlikely: Heart failure, bronchiectasis, tuberculosis, cancer, pneumothorax, lung abscess, nocardiosis, GORD, psychogenic cough

Sputum color:
- Mucoid (clear and white) often indicates no infection.
- Yellow, green, or brown sputum suggests infection.
- Mucopurulent sputum typically indicates a viral infection.
- Haemoptysis (coughing up blood) can be rust colored (pneumonia), pink tinged (left ventricular failure), or dark red (carcinoma).
Sputum nature:
- Thin and frothy sputum suggests left ventricular failure.
- Thick, mucoid to yellow sputum can indicate asthma.
- Foul-smelling sputum is associated with bronchiectasis or lung abscess.
Onset of cough:
- Cough worsening in the morning may suggest upper airways cough syndrome, bronchiectasis, or chronic bronchitis.
Duration of cough:
- Cough lasting longer than 3 weeks should be investigated further.
Periodicity of cough:
- Recurrent cough in adults may indicate chronic bronchitis, especially in smokers.
- Recurrent cough in children with a family history of eczema, asthma, or hay fever could suggest asthma.
Age of the patient:
- Children are more prone to URTIs but asthma and croup must also be considered.
- With age, conditions like bronchitis, pneumonia, and carcinoma become more prevalent.
Smoking history:
- Smokers are at higher risk for chronic and recurrent coughs, which can progress to chronic bronchitis and COPD.

Viral coughs usually begin suddenly and are associated with fever.
Sputum production is minimal, and symptoms tend to worsen in the evening.
Cold symptoms like runny nose and sore throat are often present.
Viral cough typically lasts 7 to 10 days.
Cough lasting more than 14 days might suggest postviral cough or indicate a secondary bacterial infection, but this is difficult to confirm clinically without sputum analysis.
Cough with mucopurulent sputum is generally caused by viral infection and doesn't always require immediate referral.