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For further information, see CMDT Part 2-02: Cough

Key Features

Essentials of Diagnosis

  • Inquire about

    • Age; tobacco, e-cigarette vaping, or cannabis use history; duration of cough

    • Occupational history and environmental and infection exposures

    • Dyspnea (at rest or with exertion)

    • Vital signs (temperature, respiratory rate, heart rate)

    • Chest examination findings

General Considerations

  • Cough results from stimulation of mechanical or chemical afferent nerve receptors in the bronchial tree

  • Cough illness syndromes are defined as acute (< 3 weeks), persistent (3–8 weeks), or chronic (> 8 weeks)

  • Postinfectious cough lasting 3–8 weeks also called subacute cough to distinguish this distinct clinical entity from acute and chronic cough

  • The prevalence of pertussis infection in adults with a cough lasting > 3 weeks is 20%, although exact prevalence is difficult to ascertain due to the limited sensitivity of diagnostic tests

Clinical Findings

Symptoms and Signs

  • Timing and character of cough are not very useful in establishing cause

  • However, cough-variant asthma should be considered in adults with prominent nocturnal cough, and persistent cough with phlegm increases the patient's likelihood of chronic obstructive pulmonary disease (COPD)

  • Acute cough syndromes

    • Most due to viral respiratory tract infections (eg, influenza, SARS-CoV-2)

    • Presence of post-tussive emesis or inspiratory whoop in adults modestly increases the likelihood of pertussis, and absence of paroxysmal cough and the presence of fever decreases its likelihood

    • Less common causes include heart failure (HF), hay fever (allergic rhinitis), and occupational factors

  • Search for additional features of infection such as fever, nasal congestion, and sore throat

  • Dyspnea (at rest or with exertion) may reflect a more serious condition

  • Persistent cough is usually due to

    • Angiotensin-converting enzyme (ACE) inhibitor therapy

    • Postnasal drip

    • Asthma

    • Gastroesophageal reflux disease (GERD)

  • Less common causes of persistent cough

    • Bronchogenic carcinoma

    • Chronic bronchitis

    • Bronchiectasis

    • Other chronic lung disease

    • HF

  • Chronic cough

    • Accompanied by dry eyes may suggest Sjögren syndrome

    • If dry, it may be the first symptom of idiopathic pulmonary fibrosis

  • Signs of pneumonia

    • Tachycardia

    • Tachypnea

    • Fever

    • Crackles

    • Decreased breath sounds

    • Fremitus

    • Egophony

  • Signs of acute bronchitis: wheezing and rhonchi

  • Signs of chronic sinusitis: postnasal drip

  • Signs of COPD

    • Abnormal match test (inability to blow out a match from 10 inches away)

    • Maximum laryngeal height < 4 cm (measured from the sternal notch to the cricoid cartilage at end expiration)

  • Signs of HF

    • Symmetric basilar rales

    • Abnormal jugular venous pressure

    • Positive hepatojugular reflux

Differential Diagnosis

Acute cough

  • Acute respiratory tract infection

  • Asthma

  • Allergic rhinitis

  • HF

  • ACE inhibitor therapy

Persistent cough

  • Environmental exposures (cigarette smoke, air pollution)

  • Occupational exposures

  • Pertussis, SARS-CoV-2

  • Postnasal drip

  • Asthma (including cough-variant asthma)

  • GERD

  • COPD

  • Chronic aspiration

  • Bronchiectasis, eosinophilic bronchitis

  • Tuberculosis or other chronic infection

  • Interstitial lung disease

  • Bronchogenic carcinoma



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