What is upper airway cough syndrome and how is it diagnosed?

What is Upper Airway Cough Syndrome?

Upper Airway Cough Syndrome (UACS), formerly known as postnasal drip syndrome, is a clinical syndrome where chronic cough results from upper airway conditions including allergic rhinitis, non-allergic rhinitis, chronic rhinosinusitis, or post-viral rhinitis—it represents the most common cause of both acute and chronic cough in adults. 1

Definition and Terminology

• The American College of Chest Physicians officially recommends using the term "Upper Airway Cough Syndrome" instead of "postnasal drip syndrome" because it more accurately describes the condition as a syndrome related to upper airway abnormalities rather than solely postnasal drainage 1
• UACS accounts for approximately 56% of chronic cough cases and, when combined with asthma and gastroesophageal reflux disease, represents 90% of chronic cough causes in nonsmokers with normal chest radiographs 2, 3

Pathophysiology

• The primary mechanism involves mechanical stimulation of cough receptors in the hypopharynx and larynx by secretions draining from the nose and sinuses 1
• Evidence suggests patients with UACS have heightened sensitivity of the cough reflex in the upper airway compared to normal individuals, contributing to symptom development 1
• Some researchers propose UACS represents a clinical phenotype of cough hypersensitivity syndrome, explaining why only a subset of patients with rhinitis or sinusitis develop chronic cough 4, 5

Common Underlying Causes

• Allergic rhinitis: characterized by nasal itching, sneezing, clear rhinorrhea, and seasonal patterns 6, 7
• Non-allergic rhinitis (vasomotor rhinitis): the most common upper airway disease associated with UACS, accounting for 59% of cases in one cohort 7
• Chronic rhinosinusitis: present in approximately 12% of UACS patients 7
• Post-viral rhinitis: following upper respiratory tract infections 1

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How is Upper Airway Cough Syndrome Diagnosed?

The diagnosis of UACS is fundamentally clinical and confirmed by response to specific therapy—there is no objective diagnostic test, no pathognomonic findings, and approximately 20% of patients have "silent" postnasal drip with no obvious upper respiratory symptoms yet still respond to treatment. 1, 2

Clinical Presentation to Assess

• Cardinal symptoms include sensation of something draining into the throat, frequent throat clearing, tickle in the throat, nasal congestion, or nasal discharge 1, 2
• Important caveat: Up to 20% of UACS patients are completely unaware of postnasal drainage or its connection to their cough, making the absence of these symptoms unreliable for excluding the diagnosis 1, 2
• History of recent upper respiratory infection is commonly present 1
• Patients may report hoarseness or wheeze 1

Physical Examination Findings

• Look for: mucoid or mucopurulent secretions in the posterior pharynx, cobblestone appearance of the oropharyngeal mucosa, or visible mucus in the oropharynx 1, 8
• Critical limitation: These findings are relatively sensitive but not specific—they occur in many patients with cough from other causes 1
• Pharyngeal erythema or reddish appearance represents inflammation but is nonspecific and can occur with multiple etiologies including GERD 8, 6
• A completely normal pharyngeal examination does not exclude UACS due to the phenomenon of "silent" postnasal drip 8

Diagnostic Algorithm

The American College of Chest Physicians recommends a combination approach:

1. Assess clinical features: symptoms, physical examination findings, and history of upper respiratory conditions 1

2. Consider radiographic evaluation: Sinus imaging (radiographs or CT) may be obtained if persistent nasal symptoms despite topical therapy, though mucosal thickening alone does not confirm bacterial infection requiring antibiotics 8

   • In patients with chronic cough and excess sputum production, sinus radiographs have 81% positive predictive value for UACS 8
   • In patients without excess sputum, the positive predictive value drops to 57% 8

3. Empiric therapeutic trial: This is both diagnostic AND therapeutic—the pivotal factor confirming UACS as the cause of cough 1

   • Start first-generation antihistamine/decongestant combination (e.g., dexbrompheniramine plus sustained-release pseudoephedrine) 1, 8
   • Most patients improve within days to 2 weeks of initiating therapy 8
   • Complete resolution may take several weeks to months 8
   • Response to treatment confirms the diagnosis 1, 3

Critical Diagnostic Pitfalls to Avoid

• Do not rely solely on patient awareness of postnasal drip: 20% of patients with UACS-induced cough are unaware of drainage 1, 2, 6
• Do not exclude UACS based on normal physical examination: absence of cobblestoning or visible secretions does not rule out the diagnosis 8
• Do not confuse GERD with UACS: both can cause pharyngeal inflammation and throat symptoms; they may coexist 8, 6
• Consider multiple simultaneous causes: UACS frequently coexists with asthma and GERD—maintain all partially effective treatments rather than discontinuing them prematurely 8, 6
• Recognize that symptoms and signs are nonspecific: the character and timing of cough have little diagnostic value for distinguishing UACS from other causes 1

When to Proceed with Further Evaluation

• If symptoms persist despite adequate upper airway treatment for 2 weeks, proceed with sequential evaluation for asthma/non-asthmatic eosinophilic bronchitis and gastroesophageal reflux disease 8, 2
• Consider bronchial provocation testing if spirometry is normal but asthma is suspected 8
• Obtain sinus imaging if air-fluid levels are suspected, as this indicates acute bacterial sinusitis requiring antibiotics 8