Diagnosing Postnasal Drip Syndrome (Upper Airway Cough Syndrome) Through History Taking
The diagnosis of postnasal drip syndrome (now termed Upper Airway Cough Syndrome or UACS) as the cause of chronic cough relies primarily on a combination of specific symptoms and physical findings, but importantly, the absence of these classic features does NOT rule out the diagnosis—up to 20% of patients with UACS-induced cough are completely unaware of postnasal drainage. 1
Key Historical Features to Assess
Classic Symptoms (Present in Most, But Not All Cases)
When taking a history, specifically inquire about:
- Sensation of drainage into the throat - the patient reports feeling something dripping down the back of the throat 1
- Frequent throat clearing - a persistent need to clear the throat 1
- Nasal discharge - either anterior or posterior 1
- Nasal congestion - feeling of blocked nasal passages 1
- "Tickle in the throat" - an irritating sensation in the pharynx 1
- Recent upper respiratory infection - history of a cold or similar illness preceding the cough 1
Critical Pitfall: "Silent" UACS
A major diagnostic pitfall is failing to consider UACS when classic symptoms are absent. 1 Approximately 20% of patients with UACS-induced cough have no awareness of postnasal drainage or associated upper respiratory symptoms, yet they respond to antihistamine/decongestant therapy. 1 This means you cannot rule out UACS based on history alone.
What History Does NOT Help With
The character, timing, and complications of chronic cough are NOT diagnostically useful for determining if UACS is the cause. 1, 2 Specifically:
- Cough character (dry vs. productive, harsh vs. soft) does not distinguish UACS from other causes 1, 2
- Timing of cough (morning, night, after meals) does not reliably indicate UACS 1, 2
- Presence or absence of sputum production should not be used to rule in or rule out UACS 1, 2
Multiple stepwise linear regression analysis has shown that none of the variability in cough characteristics can be explained by any specific diagnosis, including UACS. 2
Associated Symptoms to Inquire About
Beyond the classic UACS symptoms, assess for:
- Hoarseness - sometimes present with UACS 1
- Wheezing - common in UACS patients, though may indicate coexisting asthma 1
- Environmental triggers - cold air, pollutants, allergens that worsen symptoms 3
- Response to previous treatments - particularly antihistamines or decongestants 3
Differential Considerations in History
When evaluating for UACS, also inquire about symptoms suggesting alternative or coexisting diagnoses:
- Gastroesophageal reflux symptoms - GERD frequently mimics UACS and can cause upper respiratory symptoms 1
- Asthma symptoms - shortness of breath, chest tightness, wheezing 3
- ACE inhibitor use - a common medication-induced cause of chronic cough 1
- Smoking history - chronic bronchitis as alternative diagnosis 1
The Diagnostic Algorithm Based on History
Because UACS is a clinical syndrome with no pathognomonic findings, the diagnosis should be determined by considering a combination of symptoms, physical examination, radiographic findings, and ultimately response to therapy. 1
The practical approach is:
Ask about classic UACS symptoms (drainage sensation, throat clearing, nasal discharge, congestion) 1
Do NOT exclude UACS if these symptoms are absent - silent UACS occurs in 20% of cases 1
Do NOT rely on cough character or timing to make or exclude the diagnosis 1, 2
Consider empiric therapy as both diagnostic and therapeutic - improvement or resolution of cough with first-generation antihistamine/decongestant therapy confirms the diagnosis 1
Special Populations and Contexts
In patients with chronic cough and normal chest radiograph who are nonsmokers and not taking ACE inhibitors, UACS (along with asthma and GERD) accounts for approximately 90% of cases. 1, 2 In this clinical profile, UACS should be strongly considered regardless of whether classic symptoms are present. 2
Postnasal drip is recognized as the single most common cause of chronic cough. 1 In systematic studies using anatomic diagnostic protocols, UACS (including sinusitis and chronic rhinitis with postnasal drip) accounted for 56% of chronic cough cases. 4
Bottom Line for History Taking
The history for UACS should focus on identifying classic upper airway symptoms, but the absence of these symptoms does not exclude the diagnosis. 1 The character and timing of the cough itself provide no diagnostic value. 1, 2 An empiric trial of first-generation antihistamine/decongestant therapy should be considered even when the history is not suggestive, as response to treatment is the pivotal factor in confirming UACS as the cause. 1