Can a cough alone without wheezing be a sign of asthma?

Can Cough Alone Without Wheezing Be a Sign of Asthma?

While cough alone can occasionally represent asthma (termed "cough-variant asthma"), most children and adults with isolated chronic cough do not have asthma, and current guidelines strongly caution against diagnosing asthma based on cough alone. 1

Key Evidence Against Diagnosing Asthma from Cough Alone

The 2020 CHEST guidelines explicitly state that asthma should NOT be diagnosed based on the symptom of cough alone because while almost all children with asthma have intermittent cough, wheeze, and/or exercise-induced symptoms, only about 25% of children with these symptoms actually have asthma. 1

Critical Diagnostic Limitations

• Poor sensitivity and specificity: Ambulatory tracheal sound monitoring in 90 children demonstrated that cough as a marker for wheeze had sensitivity of only 34% and specificity of only 35%. 1

• Lack of airway inflammation: When airway profiles were examined in children with isolated chronic cough, studies showed very few children with airway inflammation consistent with asthma. 1

• "Cough variant asthma is probably a misnomer": A cross-sectional community study of 1,178 children found that persistent cough (>3 weeks) without wheeze differs in important respects from classic asthma and resembles the asymptomatic population. 1

When Cough-Variant Asthma Does Exist

In adults, cough-variant asthma (CVA) is a recognized entity accounting for approximately 25-42% of chronic cough cases, but it remains likely underdiagnosed. 2

Defining Characteristics of True CVA

• Chronic cough as the sole symptom without wheeze, chest tightness, or dyspnea 2
• Normal baseline pulmonary function tests 3
• Positive bronchial hyperreactivity testing (methacholine or mannitol challenge) 3, 4
• Response to specific asthma therapy (inhaled corticosteroids) 3, 4
• Higher wheezing threshold: CVA patients require greater degrees of airway obstruction before wheezing becomes audible compared to classic asthma 5

Algorithmic Approach to Isolated Cough

Step 1: Look for Additional Asthma Features

• Variable expiratory airflow limitation and symptoms that vary over time and intensity 6
• Daytime symptoms: wheeze, shortness of breath, chest tightness, exercise limitation 6
• Nocturnal symptoms: awakening with cough or wheeze 6
• Atopic features: eczema, food allergies, family history of asthma 7

Step 2: Perform Objective Testing (Age-Appropriate)

• Spirometry with bronchodilator response if the patient is old enough 6, 7
• Bronchial provocation testing (methacholine or mannitol challenge) to demonstrate hyperreactivity 3, 4
• Do NOT diagnose asthma without objective evidence 7

Step 3: Consider Alternative Diagnoses

Multiple conditions present identically to asthma with isolated cough:

• Gastroesophageal reflux disease (GERD): commonly causes nocturnal cough and wheeze 6, 8
• Sleep-disordered breathing/snoring: associated with increased nocturnal cough 6
• Protracted bacterial bronchitis (PBB): one of the most common causes of pediatric chronic cough 6
• Post-viral cough: 90% of children with viral bronchiolitis are cough-free by day 21 7
• Upper airway disorders: rhinosinusitis, though the relationship is controversial 1

Step 4: Therapeutic Trial (If Suspicion Remains High)

• Low-dose inhaled corticosteroids are the only medication class proven for long-term control 7
• Monitor carefully and stop treatment if no clear benefit within 4-6 weeks 7
• Short-acting beta-agonists like salbutamol provide symptom relief only and do not modify disease 7

Critical Pitfalls to Avoid

Over-diagnosis of asthma based on cough alone is a well-documented problem that leads to unnecessary treatment with prophylactic anti-asthma drugs. 1

• Do not treat isolated chronic cough empirically with asthma medications without other asthma symptoms or objective evidence 7
• Persistent cough and recurrent chest colds without wheeze should not be considered a variant of asthma 1
• Atopy markers (skin prick test, specific IgE) are unlikely to determine which children with cough will respond to asthma therapies 1
• Nocturnal symptom reporting is unreliable, with subjective reports correlating poorly with objective cough counts (Cohen's kappa 0.3) 6

Bottom Line for Clinical Practice

Require objective evidence of bronchial hyperreactivity and/or response to asthma-specific therapy before diagnosing cough-variant asthma. 3, 4 The presence of cough alone, even if chronic or nocturnal, does not justify an asthma diagnosis or empiric asthma treatment without additional supporting features or testing. 1, 7