In a 35-year-old woman with a 30‑day productive cough, how should I diagnose upper airway cough syndrome (UACS)?

How to Diagnose Upper Airway Cough Syndrome

UACS is a clinical diagnosis based on a combination of symptoms, physical examination findings, and—most importantly—response to empiric therapy with first-generation antihistamine/decongestant combinations, as there is no objective test or pathognomonic finding that confirms the diagnosis. 1

Understanding the Diagnostic Challenge

UACS (formerly called postnasal drip syndrome) has no objective diagnostic test and no way to quantify or directly prove that upper airway secretions are causing the cough. 1 Because improvement or resolution of cough in response to specific treatment is the pivotal factor in confirming the diagnosis, an empiric trial of therapy is both diagnostic and therapeutic. 1

Approximately 20% of patients with UACS are completely unaware of postnasal drainage or its connection to their cough—this is termed "silent" UACS. 1 Therefore, the absence of classic upper airway symptoms does not rule out UACS. 1

Clinical Features to Assess

Symptoms (Present in Most but Not All Cases)

• Sensation of something dripping down into the throat 1, 2
• Frequent throat clearing or need to clear phlegm 1, 2
• Nasal discharge or congestion 1, 2
• Tickle sensation in the throat 1
• History of recent upper respiratory infection 1

Critical caveat: The character, timing, or productivity of the cough should NOT be used to rule in or rule out UACS—these features are unreliable and non-specific. 1

Physical Examination Findings

• Cobblestone appearance of the oropharyngeal mucosa 1, 2
• Visible mucus in the oropharynx or posterior pharynx 1, 2
• Mucopurulent secretions on examination of the nasopharynx 1

Important limitation: These physical findings are relatively sensitive but NOT specific—they are also found in many patients with cough from other causes. 1

Diagnostic Algorithm

Step 1: Initial Clinical Assessment

Ensure the patient meets basic criteria for chronic cough evaluation: 1

• Normal chest radiograph
• Non-smoker (or former smoker with normal imaging)
• Not taking an ACE inhibitor

Step 2: Empiric Therapeutic Trial (First-Line Diagnostic Approach)

Start a first-generation antihistamine/decongestant combination immediately as the primary diagnostic maneuver. 1, 2 This approach should be used even when a specific etiology is not apparent, before beginning extensive diagnostic workup. 1

Recommended regimens include: 2

• Dexbrompheniramine 6 mg + pseudoephedrine 120 mg (sustained-release) twice daily
• Brompheniramine 12 mg twice daily
• Chlorpheniramine 4 mg four times daily

Critical point: First-generation antihistamines work through their anticholinergic properties, NOT their antihistamine effects. 2 Second-generation antihistamines (loratadine, fexofenadine, cetirizine) are completely ineffective for UACS because they lack anticholinergic activity. 1, 2

Step 3: Assess Response at 1-2 Weeks

If cough improves or resolves: The diagnosis of UACS is confirmed. 1, 2 Continue treatment as directed for the underlying upper airway condition.

If cough persists after 2 weeks of appropriate therapy: Proceed to sinus imaging. 1

Step 4: Sinus Imaging for Non-Responders

Order CT scan of the sinuses if empiric antihistamine/decongestant therapy fails. 1

Important caveat: Chronic sinusitis may cause cough that is relatively or completely nonproductive, with none of the typical findings of acute sinusitis present—it can be clinically silent. 1 However, sinus CT abnormalities have low positive predictive value (67%) for UACS, meaning upper airway disease frequently coexists but does not always contribute to cough. 3

Step 5: Consider Multiple Coexisting Causes

UACS, asthma, and GERD together account for 90% of chronic cough causes, and multiple conditions frequently coexist. 1, 4 In all patients with chronic cough, regardless of clinical signs or symptoms, each of these diagnoses must be considered because they can each present as isolated cough with no other findings ("silent UACS," "cough variant asthma," "silent GERD"). 1

If UACS treatment fails and sinus imaging is negative or treatment of identified sinus disease doesn't resolve cough: 2

• Consider GERD (empiric PPI trial for 8 weeks)
• Consider asthma (methacholine challenge or empiric inhaled corticosteroids)

Common Diagnostic Pitfalls

Do not rely on cough characteristics: Productive versus nonproductive cough, timing, or character cannot distinguish UACS from other causes. 1

Do not assume absence of upper airway symptoms rules out UACS: Up to 20% of UACS patients have no awareness of postnasal drainage. 1

Do not over-interpret sinus CT findings: Abnormalities on sinus imaging do not always correlate with cough causation. 3

Do not use second-generation antihistamines: They are ineffective for UACS and should not be used for diagnostic or therapeutic purposes. 1, 2

Do not evaluate in isolation: Always consider that UACS may coexist with asthma and GERD, particularly in patients who only partially respond to initial therapy. 1, 4