Respiratory

Chronic cough: outpatient diagnostic algorithm

Clinical Overview and When to Suspect Chronic Cough

— Upper airway cough syndrome (UACS) — formerly postnasal drip

— Asthma / cough-variant asthma

— GERD (often non-acid or silent reflux)

— Smoker or ex-smoker → chronic bronchitis, COPD, lung cancer

— On ACE inhibitor → drug-induced (5–35% incidence, can begin weeks to months after start)

— Hemoptysis, weight loss, night sweats, fever → TB, malignancy, bronchiectasis

— Occupational/environmental exposures → hypersensitivity pneumonitis, asbestosis

— Progressive dyspnea, Velcro crackles → ILF/ILD

— Copious purulent sputum → bronchiectasis

— Dysphagia, aspiration risk → laryngeal/neurologic etiology

Definition (adults): cough lasting >8 weeks. Subacute = 3–8 weeks (often post-infectious). Acute = <3 weeks.

Epidemiology: affects ~10% of US adults; one of the top 5 reasons for outpatient visits. Disproportionately affects women (heightened cough reflex) and patients age 40–60.

Three dominant outpatient causes in immunocompetent, non-smoking adults with a normal CXR (the "Big 3"):

Together these account for >90% of chronic cough in this population, and >25% of patients have ≥2 contributors simultaneously — a critical Step 3 concept.

When to suspect a non-Big-3 etiology (move workup earlier):

Step 3 management: the outpatient algorithm is sequential and empiric — confirm cough duration, stop any ACE inhibitor, obtain CXR, then treat the most likely Big-3 cause for 2–4 weeks before escalating. Do not order CT, bronchoscopy, or PFTs as initial tests in an uncomplicated patient.

Board pearl: the single most cost-effective first action in a patient on lisinopril with chronic cough is to discontinue the ACE inhibitor and reassess in 4 weeks — cough may persist up to 4 weeks after stopping. Switching to an ARB is appropriate if ongoing RAAS blockade is needed.

Presentation Patterns and Key History

— Duration (confirm true chronicity ≥8 weeks; many "chronic" coughs are actually subacute post-infectious)

— Smoking status (current, pack-years, secondhand, vaping)

— Medication review — ACEi, sitagliptin (rare), topical beta-blocker eye drops

— Occupational/environmental — dust, molds, birds, hot tubs, cleaning chemicals

— Travel/TB exposure, homelessness, incarceration, HIV risk

— Allergic phenotype — seasonal rhinitis, eczema, atopy → UACS or asthma

— GERD features — heartburn, regurgitation, sour taste, worse supine or postprandial (but silent reflux in 40–75% of GERD-cough)

— Asthma features — nocturnal cough, exercise-triggered, cold-air or laughter-triggered wheeze

— Red flags — hemoptysis, fever, weight loss >5%, dyspnea, dysphagia, hoarseness >3 weeks

— Cough worse lying down → UACS (drip) or GERD

— Cough after eating/talking → GERD or laryngeal sensory neuropathy

— Seasonal, worse with cold air/exercise → asthma

— Throat clearing, "drip" sensation, nasal congestion → UACS

— Productive most mornings, smoker → chronic bronchitis (≥3 months/yr × 2 yrs)

Cough character is unreliable for etiology (dry vs productive, timing, "tickle") — multiple trials show poor predictive value. Focus instead on associated features and exposures.

History elements that drive the algorithm:

Pattern clues (suggestive, not diagnostic):

Cough hypersensitivity syndrome — emerging concept where triggers (perfumes, talking, temperature change) provoke cough via afferent neural sensitization; consider after Big 3 excluded.

Key distinction: post-infectious cough (3–8 weeks after viral URI, often with transient bronchial hyperreactivity) is subacute and usually self-limited — distinguish from true chronic cough to avoid over-investigation. Empiric inhaled ipratropium or short ICS course often suffices.

Board pearl: always re-confirm tobacco cessation; even reduced smoking can convert chronic cough to subacute resolution within 4 weeks of full cessation.

Physical Exam Findings (and Targeted Assessment)

— Cobblestoning of posterior oropharynx, mucoid drip → UACS

— Boggy/pale turbinates → allergic rhinitis; erythematous → vasomotor or infectious

— Sinus tenderness, purulent discharge → chronic rhinosinusitis

— Tonsillar hypertrophy, uvular edema → consider OSA-related cough

— Laryngeal erythema, posterior cobblestoning, vocal cord edema on flexible scope → laryngopharyngeal reflux

— Wheezing (may be absent in cough-variant asthma — auscultate after forced expiration)

— Inspiratory "Velcro" crackles at bases → IPF

— Localized crackles → pneumonia, bronchiectasis

— Stridor → tracheal/laryngeal pathology

— Hyperresonance, prolonged expiration → COPD

Chronic cough is largely a history-driven diagnosis, but a focused exam narrows the differential and identifies red flags.

Vital signs: resting SpO₂ <94%, tachypnea, or fever shifts the workup toward parenchymal disease (pneumonia, ILD, TB, malignancy) — not Big 3.

HEENT:

Neck: lymphadenopathy (TB, malignancy, sarcoid), thyromegaly (compressive cough), tracheal deviation.

Cardiac: displaced PMI, S3, elevated JVP → consider cardiogenic cough from HF/pulmonary congestion (often missed cause).

Pulmonary:

Skin/joints: clubbing (ILD, bronchiectasis, lung CA), eczema/atopy, sclerodactyly (CTD-ILD), Gottron papules (dermatomyositis-ILD).

Neuro: bulbar dysfunction, weak cough, abnormal swallow → aspiration cough; vagal nerve dysfunction.

Step 3 management: if exam reveals clubbing, weight loss, hemoptysis, or focal lung findings, skip the empiric Big-3 trial pathway and proceed directly to CT chest and pulmonology referral. Empiric therapy is reserved for the well-appearing patient with a normal CXR and no red flags.

Board pearl: a patient with chronic cough, basilar Velcro crackles, and clubbing has IPF until proven otherwise — order HRCT chest, not empiric PPI.

Diagnostic Workup — Initial Labs / Imaging

— Stop the ACE inhibitor (if applicable) and reassess in 4 weeks

— Smoking cessation counseling and exposure removal

— Obtain a CXR (PA and lateral) — this is the universal initial imaging study

— CBC if infection, malignancy suspected

— HIV test if risk factors

— IGRA/TB skin test if exposure risk

— Sputum AFB ×3 if cough >3 weeks + risk factors or imaging concern

— Eosinophil count, total IgE if atopic/asthma phenotype unclear

— BNP if HF suspected

— FEV₁/FVC <0.70 with ≥12% and 200 mL reversibility → asthma

— Normal spirometry does not exclude cough-variant asthma — proceed to methacholine challenge or empiric ICS trial

— Abnormal CXR

— Hemoptysis, weight loss, persistent fever

— Smoker >30 pack-years or age >40 with persistent cough

— Suspected bronchiectasis, ILD, or malignancy

The first three steps in every adult with chronic cough (normal exam, no red flags):

CXR purposes: rule out malignancy, TB, bronchiectasis, ILD, cardiomegaly/HF, foreign body, mediastinal mass. A normal CXR unlocks the empiric Big-3 algorithm.

Labs are NOT routine. Order selectively:

Spirometry with bronchodilator response is appropriate early when asthma is suspected:

No initial role for: CT chest, bronchoscopy, esophageal pH/impedance, PFTs beyond spirometry, or ENT laryngoscopy in uncomplicated cases.

Indications to escalate imaging to CT chest early:

CCS pearl: in the CCS case of a 55-year-old smoker with 8-week cough, the highest-yield orders are CXR, spirometry, smoking cessation counseling, and low-dose CT lung cancer screening (if 50–80 yo, ≥20 pack-yr, current or quit <15 yr) — not empiric PPI.

Board pearl: never accept a "normal chest exam" as a substitute for CXR in chronic cough — it is the mandatory first imaging study regardless of exam findings.

Diagnostic Workup — Advanced or Confirmatory Studies

— Indicated when asthma is suspected but spirometry is normal

— PC20 <8 mg/mL = airway hyperresponsiveness consistent with asthma

— Negative test essentially excludes asthma (high NPV ~100%) — its main clinical utility

— >50 ppb → eosinophilic airway inflammation, predicts ICS response

— Useful for non-asthmatic eosinophilic bronchitis (NAEB) — normal spirometry, normal challenge, but sputum eosinophils >3%; responds to ICS

— 24-hour pH/impedance monitoring off PPI → detects acid and non-acid reflux

— Manometry if dysmotility suspected

— EGD not first-line for cough alone

When the empiric Big-3 trial fails or red flags emerge, escalate in stepwise fashion:

HRCT chest: for suspected bronchiectasis, ILD, atypical infection, or unexplained persistent cough despite full Big-3 therapy. HRCT is the gold standard for bronchiectasis and IPF.

Methacholine bronchoprovocation challenge:

FeNO (fractional exhaled nitric oxide):

Esophageal studies for refractory GERD-cough:

Laryngoscopy (ENT referral): vocal cord dysfunction, laryngopharyngeal reflux, paradoxical vocal fold motion, tumor.

Bronchoscopy: reserved for suspected foreign body, endobronchial lesion, hemoptysis, or unexplained focal CT finding.

Sputum induction with differential cell count: identifies NAEB and eosinophilic asthma when available.

Echocardiogram: if HF or pulmonary hypertension suspected.

Step 3 management: when all Big-3 trials fail and HRCT/spirometry/methacholine/pH study are unrevealing, label as "refractory or unexplained chronic cough" and refer to a cough specialty clinic. Emerging therapies include gefapixant (P2X3 antagonist, approved in some regions), low-dose morphine, gabapentin, pregabalin, and speech-language pathology cough-suppression therapy.

Board pearl: a patient with chronic cough, normal CXR, normal spirometry, negative methacholine, and elevated FeNO + sputum eosinophils → non-asthmatic eosinophilic bronchitis — treat with inhaled corticosteroid.

Risk Stratification and Empiric Treatment Logic

— Stop ACE inhibitor → reassess at 4 weeks

— Smoking/vaping/exposure cessation

— CXR

— Predominant nasal/drip symptoms → treat UACS first

— Wheeze, nocturnal, exercise trigger → treat asthma first

— Reflux symptoms or no clear clue → lifestyle + consider PPI, though evidence for empiric PPI in absence of typical GERD symptoms is weak (recent ACCP guidelines do NOT recommend empiric PPI without GERD features)

— No clear clue: start with UACS empiric therapy (highest pretest probability in non-atopic adults)

— UACS (1st-gen antihistamine/decongestant): 2 weeks

— Asthma (ICS ± LABA): 4–8 weeks

— GERD (PPI BID + lifestyle): 8–12 weeks (longer due to slower response)

The outpatient chronic cough algorithm is sequential, empiric, and time-limited. Each trial is a diagnostic-therapeutic test:

Step 1 — Universal interventions (all patients):

Step 2 — Empiric trial for the most likely Big-3 cause based on history:

Step 3 — Sequential trials: if no response after 2–4 weeks, add therapy for next most likely cause rather than switching, because multiple etiologies coexist in ~25% of patients.

Step 4 — Reassess and investigate if all three trials fail: HRCT, methacholine, FeNO, pH study, ENT, pulmonology.

Duration of each trial:

CCS pearl: advance the simulation clock by 2–4 weeks after each empiric trial. Re-evaluate cough diary, symptom score, and side effects. If improved, continue therapy for the full course; if no change, add the next empiric trial without stopping the previous one (unless side effects).

Key distinction: "refractory chronic cough" requires that all three Big-3 causes have been adequately treated and excluded — premature labeling leads to overuse of opioids and neuromodulators.

Pharmacotherapy — Empiric Regimens for the Big 3

— First-generation antihistamine + decongestant is the diagnostic empiric trial of choice (e.g., chlorpheniramine or brompheniramine + pseudoephedrine) for 2 weeks — works via anticholinergic effect on mucosal secretions

— Non-sedating 2nd-gen antihistamines (loratadine, cetirizine) are less effective for non-allergic UACS but preferred if allergic rhinitis is established

— Intranasal steroid (fluticasone, mometasone) for allergic rhinitis or chronic rhinosinusitis — 4-week trial

— Intranasal ipratropium for vasomotor rhinitis

— Saline nasal irrigation as adjunct

— Inhaled corticosteroid (e.g., fluticasone 100–250 mcg BID) is first-line — trial 4–8 weeks

— Add LABA (formoterol/salmeterol) if inadequate response — now preferred as ICS-formoterol SMART therapy per GINA

— Leukotriene receptor antagonist (montelukast) as add-on; counsel on FDA black-box warning for neuropsychiatric effects

— Oral prednisone burst rarely needed for diagnostic clarification

— Lifestyle first: weight loss, elevate head of bed, avoid late meals, reduce alcohol/caffeine/chocolate/fatty foods

— PPI BID (omeprazole 20 mg BID, 30 min before meals) for 8–12 weeks if GERD symptoms present

— Add H2 blocker at bedtime for nocturnal symptoms

— Prokinetic (metoclopramide) only if dysmotility documented — beware tardive dyskinesia

— Anti-reflux surgery (Nissen) reserved for proven refractory acid reflux

Upper Airway Cough Syndrome (UACS):

Asthma / Cough-variant asthma:

GERD-related cough:

Non-asthmatic eosinophilic bronchitis: ICS, same dosing as asthma.

Step 3 management: counsel that cough response lags symptom response — GERD cough may take 8–12 weeks to resolve even when reflux is controlled. Do not abandon a trial prematurely.

Board pearl: newer 2nd-gen antihistamines are inferior to 1st-gen for UACS-related cough because the therapeutic effect is anticholinergic, not antihistaminic.

Expanded Pharmacology — Refractory and Adjunctive Therapy

— Gabapentin 300 mg daily titrated to 1800 mg/day divided — randomized trial evidence supports use; monitor for somnolence, dizziness, weight gain

— Pregabalin alternative

— Amitriptyline 10–25 mg qHS — particularly for post-viral neuropathic cough

— Tramadol or low-dose morphine (5–10 mg BID) — last resort, controlled-substance risks, requires REMS-style counseling

— Gefapixant approved in Japan, EU; FDA non-approval in US (2022) but actively under review — selectively inhibits ATP-mediated airway sensory nerve activation. Side effect: taste disturbance/dysgeusia in ~60%.

— Inhaled ipratropium for post-infectious bronchial hyperreactivity

— Inhaled lidocaine — specialty use only

— Speech-language pathology cough-suppression therapy (PSALTI protocol) — education, laryngeal hygiene, cough-control breathing, psychoeducation — evidence-based, recommended by ACCP and ERS

— Pulmonary rehab if deconditioning

— Dextromethorphan OTC — modest benefit in acute/subacute cough; little for chronic

— Benzonatate 100–200 mg TID — local anesthetic on stretch receptors; warn about chewing/sucking → fatal in children and risk of laryngospasm

— Codeine — limited evidence, controlled substance

— Honey — useful in pediatric acute cough only; not for <1 year (botulism risk)

When Big-3 trials fail and workup is unrevealing, the diagnosis is refractory or unexplained chronic cough (RCC/UCC) — a cough hypersensitivity phenotype.

Neuromodulators (off-label, modest evidence):

P2X3 receptor antagonists (emerging class):

Inhaled agents:

Non-pharmacologic — first-line for RCC:

Antitussives (symptom-only, do not modify disease):

Step 3 management: before starting a neuromodulator or opioid for chronic cough, document failure of all Big-3 empiric trials, normal HRCT, normal spirometry/methacholine, and completion of speech therapy referral. This protects against opioid overuse and meets standard-of-care expectations.

Board pearl: benzonatate capsules must be swallowed whole — chewing causes oropharyngeal anesthesia, choking, and reported deaths, especially in children.

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher prevalence of multi-etiology cough (≥2 causes in up to 50%)

— HF-related cough is underrecognized — check BNP, echo if exertional dyspnea, orthopnea

— Aspiration from dysphagia, stroke, Parkinson disease, dementia — bedside swallow + SLP eval

— Chronic micro-aspiration may present as chronic cough without overt choking

— Polypharmacy: ACEi, sitagliptin, methotrexate (pneumonitis), amiodarone (pulmonary toxicity), nitrofurantoin (chronic interstitial pneumonitis) — review every medication

— Lung cancer risk rises sharply — low threshold for CT chest in any smoker >50 with new persistent cough

— OSA may cause chronic cough via reflux and airway inflammation; screen with STOP-BANG

— 1st-gen antihistamines carry strong anticholinergic burden — Beers Criteria caution in adults ≥65 (confusion, falls, urinary retention, glaucoma exacerbation). Prefer intranasal ipratropium or intranasal steroid instead

— Decongestants (pseudoephedrine) — avoid in uncontrolled HTN, CAD, BPH, hyperthyroidism, narrow-angle glaucoma

— PPI — long-term risks magnified in elderly: C. difficile, fractures, hypomagnesemia, B12 deficiency, AKI from interstitial nephritis, possible dementia association — use lowest effective dose, shortest duration

— Gabapentin — renal dose adjustment: CrCl 30–60 → max 1400 mg/day; CrCl <30 → max 700 mg/day; further reduction on HD

— Codeine/tramadol — avoid in elderly (Beers), CYP2D6 variability, fall risk

— Avoid acetaminophen-containing combinations >2 g/day in chronic liver disease

— Use caution with sedating antihistamines and opioids

Elderly considerations:

Drug dosing adjustments:

Hepatic impairment:

Step 3 management: in an 78-year-old with chronic cough on lisinopril, amlodipine, and metformin, the single highest-yield action is to stop lisinopril and reassess at 4 weeks before adding antihistamines that risk delirium and falls.

Board pearl: any patient on amiodarone with new chronic cough → suspect amiodarone pulmonary toxicity — order CXR, HRCT, PFTs with DLCO.

Special Populations — Pregnancy and Pediatrics

— CXR with abdominal shielding is safe (fetal dose <0.01 mGy) — do not withhold for chronic cough workup

— Avoid ACE inhibitors and ARBs (teratogenic, especially 2nd/3rd trimester) — should already be stopped pre-pregnancy

— UACS: intranasal steroids (budesonide is preferred, Cat B historically), nasal saline; avoid 1st-gen antihistamines with strong anticholinergic effects late in pregnancy; chlorpheniramine and loratadine considered acceptable

— Pseudoephedrine avoid in 1st trimester (gastroschisis association)

— Asthma: ICS (budesonide preferred), SABA (albuterol), LABA add-on if needed — uncontrolled asthma is more dangerous to fetus than asthma medications

— GERD: lifestyle first; calcium carbonate, sucralfate first-line; H2 blockers (ranitidine withdrawn; famotidine acceptable); PPIs (omeprazole, others) considered safe if needed

— Avoid codeine, benzonatate, gabapentin without clear indication

— Pertussis — vaccinate with Tdap at 27–36 weeks every pregnancy; consider pertussis in any pregnant patient with paroxysmal cough

— Different "Big 3": protracted bacterial bronchitis (PBB), asthma, and upper airway pathology (adenoid hypertrophy, sinusitis)

— GERD is a less common cause than in adults

— Always consider foreign body aspiration in toddlers with abrupt-onset cough — inspiratory/expiratory or decubitus CXR, bronchoscopy

— Habit/tic cough — daytime only, disappears with sleep or distraction

— Cystic fibrosis — sweat chloride if recurrent infections, failure to thrive, steatorrhea

— Pertussis, TB, primary ciliary dyskinesia in appropriate contexts

— Avoid codeine and OTC cough/cold products in <4 years (FDA); honey for >1 year only

— Avoid promethazine in <2 years (fatal respiratory depression)

Pregnancy:

Pediatrics (chronic cough = >4 weeks in children):

Step 3 management: a 2-year-old with 3 weeks of wet cough responding to amoxicillin-clavulanate likely had protracted bacterial bronchitis — confirm by 2-week antibiotic trial response.

Board pearl: never give honey to an infant <12 months — botulism risk.

Complications and Adverse Outcomes

— Cough syncope — increased intrathoracic pressure → reduced venous return → cerebral hypoperfusion. Driving restriction implications.

— Rib fractures — especially in osteoporosis, chronic steroid use; consider DEXA

— Vertebral compression fractures

— Abdominal/inguinal hernias, urinary stress incontinence (40–60% of women with chronic cough)

— Subconjunctival hemorrhage, epistaxis, petechiae

— Pneumothorax, pneumomediastinum (rare)

— Hoarseness, laryngeal trauma

— Headache, dizziness

— Social isolation, embarrassment, work absenteeism

— Depression, anxiety — bidirectional relationship with cough hypersensitivity

— Sleep disturbance for patient and partner

— Decreased health-related quality of life scores comparable to severe COPD

— PPI long-term: C. difficile, fractures, hypomagnesemia, B12 deficiency, AKI/CKD, pneumonia risk

— ICS: oral candidiasis, dysphonia, cataracts, osteoporosis with high dose

— 1st-gen antihistamines: anticholinergic burden, falls, delirium, urinary retention

— Decongestants: hypertension, arrhythmia, urinary retention

— Opioid antitussives: dependence, constipation, respiratory depression

— Missed lung cancer

— Missed TB → community transmission, public health implications

— Untreated bronchiectasis → progressive lung function decline

— Untreated IPF → loss of antifibrotic window

Chronic cough is rarely life-threatening itself, but produces substantial morbidity, complications, and quality-of-life burden.

Mechanical complications of cough paroxysms:

Psychosocial:

Iatrogenic complications from prolonged empiric therapy:

Complications from delayed diagnosis:

Step 3 management: in a 60-year-old woman with chronic cough complaining of urinary leakage with each paroxysm, diagnose and treat the cough cause and refer for pelvic floor PT simultaneously — both interventions improve continence.

Board pearl: cough syncope mandates the same driving restrictions as other syncope causes in many states; document counseling.

When to Escalate Care — Specialty Referral and Inpatient Triage

— Failure of all three Big-3 empiric trials adequately delivered

— Abnormal CXR/CT findings (nodule, mass, ILD, bronchiectasis)

— Suspected asthma with normal spirometry needing methacholine

— Suspected ILD, sarcoidosis, hypersensitivity pneumonitis

— Bronchiectasis, recurrent pulmonary infections

— Need for bronchoscopy

— Suspected chronic rhinosinusitis refractory to medical therapy

— Hoarseness >3 weeks (always exclude laryngeal cancer — smoker, alcohol)

— Vocal cord dysfunction, paradoxical vocal fold motion

— Suspected laryngopharyngeal reflux for laryngoscopy

— Refractory GERD after 12 weeks of optimized PPI BID

— Need for pH/impedance monitoring or manometry

— Evaluation for fundoplication

— Difficult allergic rhinitis, suspected aspirin-exacerbated respiratory disease, immunodeficiency with recurrent infections

— Hemoptysis (any volume), unexplained weight loss, new clubbing, persistent focal findings

— Massive hemoptysis (>200 mL/24 h) → ICU, IR, bronchoscopy

— Hypoxia (SpO₂ <90%), severe respiratory distress

— Suspected active pulmonary TB requiring airborne isolation pending sputum AFB

— Severe complications (pneumothorax, vertebral fracture with neuro deficit)

— Cough syncope with injury or recurrent episodes

Most chronic cough is managed entirely outpatient by primary care. Escalation is needed in defined scenarios.

Refer to pulmonology when:

Refer to ENT when:

Refer to GI when:

Refer to allergy/immunology when:

Refer to oncology/urgent CT when:

Inpatient admission indicators (rare for cough alone):

CCS pearl: for suspected active TB, order respiratory isolation (airborne, negative-pressure room), 3 sputum AFB smears 8 hours apart with at least 1 early-morning, NAAT, IGRA or TST, HIV test, and notify the public health department — mandatory reportable disease.

Board pearl: hemoptysis with chronic cough in a smoker = CT chest + bronchoscopy, not another empiric trial.

Key Differentials — Pulmonary and Airway Causes

— Cough may be sole symptom; spirometry often normal; methacholine challenge confirms; responds to ICS

— Normal spirometry, negative methacholine, but elevated sputum eosinophils >3% and high FeNO; ICS-responsive

— Smoker, productive morning cough, FEV₁/FVC <0.70 post-bronchodilator

— Daily mucopurulent sputum, recurrent infections, hemoptysis; HRCT shows airway dilation, tram-tracking, signet-ring sign; workup CF, immunodeficiency, ABPA, NTM, primary ciliary dyskinesia

— Dry cough, progressive dyspnea, Velcro crackles, clubbing; HRCT diagnostic

— Change in chronic cough character, hemoptysis, weight loss — CT chest mandatory in smokers >40

— Risk factors, weight loss, night sweats, cavitary or upper-lobe disease; MAC in Lady Windermere syndrome (elderly thin women, RML/lingula bronchiectasis)

— 3–8 weeks after viral URI or pertussis; airway hyperreactivity; usually self-limited

— Paroxysmal cough with inspiratory whoop, post-tussive emesis; PCR or culture; azithromycin treats but mainly reduces transmission; reportable

— Bird, mold, hot-tub exposure; HRCT mosaic attenuation, centrilobular nodules

— Sudden onset, focal wheeze; bronchoscopy diagnostic

— Inspiratory stridor mimicking asthma; laryngoscopy diagnostic

Within the respiratory system, multiple causes mimic Big-3 chronic cough:

Asthma / cough-variant asthma:

Non-asthmatic eosinophilic bronchitis (NAEB):

COPD / chronic bronchitis:

Bronchiectasis:

Interstitial lung disease (IPF, HP, CTD-ILD, sarcoidosis):

Lung cancer:

Tuberculosis / non-tuberculous mycobacteria:

Post-infectious cough:

Pertussis (whooping cough):

Hypersensitivity pneumonitis:

Foreign body:

Vocal cord dysfunction / paradoxical vocal fold motion:

Tracheomalacia, tracheobronchomegaly, endobronchial tumors: dynamic CT or bronchoscopy

Key distinction: NAEB vs cough-variant asthma — both eosinophilic and ICS-responsive, but NAEB has no bronchial hyperresponsiveness on methacholine; NAEB does not progress to fixed obstruction.

Key Differentials — Non-Pulmonary Causes

— Even silent reflux (40–75% lack heartburn); diagnosis confirmed with empiric PPI response or 24-h pH/impedance off PPI

— Allergic rhinitis, non-allergic rhinitis, vasomotor rhinitis, chronic rhinosinusitis, anatomic nasal obstruction

— Bradykinin/substance P accumulation; 5–35% of users; may begin weeks to months after starting; resolves within 1–4 weeks of stopping; ARBs do NOT cause this — appropriate switch

— Sitagliptin (DPP-4 inhibitors), methotrexate (pneumonitis), amiodarone (pulmonary toxicity), nitrofurantoin (chronic interstitial pneumonitis), beta-blocker eye drops in asthmatics, inhaled drugs (irritant)

— Heart failure (especially nocturnal cough, orthopnea); mitral stenosis with pulmonary congestion or left atrial enlargement compressing left mainstem bronchus (Ortner syndrome); pulmonary embolism (rare)

— Dysphagia, stroke, Parkinson, Zenker diverticulum, achalasia, tracheoesophageal fistula

— Arnold nerve reflex — auricular branch of vagus stimulated by cerumen impaction, foreign body, or hair touching the tympanic membrane → reflex cough; otoscopy diagnostic, cerumen removal curative

— Thyroid goiter, lymphadenopathy, aortic aneurysm, vascular ring

— More common in adolescents; absent during sleep; diagnosis of exclusion

— Triggers like perfumes, talking, temperature changes; responds to neuromodulators and speech therapy

Beyond the airways, chronic cough has multiple extra-pulmonary etiologies:

GERD / laryngopharyngeal reflux:

Upper airway cough syndrome (UACS):

ACE inhibitor cough:

Other medications:

Cardiovascular:

Aspiration:

Otologic:

Mediastinal/extrinsic compression:

Psychogenic/habit cough:

Cough hypersensitivity syndrome / neuropathic cough:

Tic-related cough (Tourette spectrum): vocal tic phenomenology

Somatic cough disorder: DSM-5 framework for functional cough

Board pearl: the Arnold nerve reflex (ear-canal stimulation triggers cough) is a classically tested zebra — always look in the ears of a patient with unexplained chronic cough.

Secondary Prevention and Long-Term Plan

— Offer all 5 A's (Ask, Advise, Assess, Assist, Arrange)

— Combine pharmacotherapy: varenicline (most effective), bupropion, nicotine replacement (patch + gum/lozenge combination)

— Refer to quitlines (1-800-QUIT-NOW)

— Influenza annually

— Tdap once in adulthood, then Td every 10 years; Tdap each pregnancy 27–36 weeks

— Pneumococcal — PCV20 alone or PCV15 + PPSV23 in adults ≥65 or younger with chronic lung disease

— COVID-19 per current CDC schedule

— RSV in adults ≥75 (and 60–74 high-risk) per ACIP

— Asthma: ICS-formoterol SMART therapy per GINA; written asthma action plan; trigger avoidance; allergen immunotherapy if appropriate

— GERD: lifestyle (weight loss is highest-impact intervention), head-of-bed elevation, meal timing; lowest effective PPI dose; periodic step-down trials

— UACS/rhinitis: intranasal steroid maintenance, allergen avoidance, immunotherapy

— COPD: LAMA/LABA ± ICS by GOLD stage; pulmonary rehab; oxygen if SpO₂ <88%

— Bronchiectasis: airway clearance (Acapella, vest), pulmonary hygiene, treat exacerbations promptly

Once the cause is identified and treated, the long-term goal is prevention of recurrence and protection of pulmonary health.

Smoking cessation: the single most impactful intervention for any patient with chronic cough.

Vaccination — secondary prevention against cough-causing infections:

Disease-specific maintenance:

Environmental: remove indoor allergens, mold remediation, dust mite covers, HEPA filtration, occupational exposure mitigation.

Step 3 management: for any patient with chronic cough on chronic PPI, plan a step-down trial at 12 weeks — taper to once daily, then on-demand or H2 blocker, to minimize long-term PPI-associated harms while maintaining symptom control.

Board pearl: weight loss of ≥10% body weight reduces GERD symptoms more than any drug — counsel directly.

Follow-Up, Monitoring, and Counseling

— 2–4 weeks after each Big-3 trial: assess cough frequency/severity (validated tools: Leicester Cough Questionnaire, Cough Visual Analog Scale, Cough Severity Diary)

— 4 weeks after ACEi discontinuation

— 8–12 weeks for GERD/PPI trial response

— Annual monitoring once stable: lung function (if asthma/COPD), medication review, vaccination status

— Inhaler technique is the #1 cause of "treatment failure" in asthma — observe and re-educate at every visit; consider spacer with MDI

— PPI must be taken 30–60 minutes before the first meal — common counseling miss

— Intranasal steroid: aim laterally away from septum to prevent epistaxis

— Expected timeline (cough improves slowly even when cause is treated)

— Side-effect surveillance

— Smoking cessation re-addressed at every visit

— Environmental triggers and avoidance

— Vocal hygiene, hydration, voice rest if laryngeal irritation

— Pelvic floor exercises if stress incontinence

Follow-up cadence is built into the empiric algorithm:

Cough diary: patients should track frequency, triggers, sputum, response to therapy — improves both diagnosis and adherence.

Adherence and technique:

Counseling topics:

Speech-language pathology cough-suppression therapy: evidence-based for refractory cough; multi-session program teaching laryngeal hygiene, cough-control breathing, and education.

Pulmonary rehabilitation: for COPD, bronchiectasis, ILD, post-COVID — improves cough-related QOL.

Mental health: screen for depression/anxiety (PHQ-9, GAD-7) — bidirectional with chronic cough; treat actively.

Step 3 management: at the 4-week follow-up after an empiric ICS trial, if cough is improved but not resolved, continue ICS and add the next Big-3 trial (e.g., PPI or antihistamine), rather than stopping the partial responder — because multiple etiologies commonly coexist.

Board pearl: always re-observe inhaler technique at follow-up — "treatment failure" is often "technique failure."

Ethical, Legal, and Patient Safety Considerations

— Any confirmed (and in most states, suspected) pulmonary TB is reportable to state/local health departments

— Initiate airborne isolation before confirmation if clinical suspicion is high

— Directly observed therapy (DOT) is the public-health standard

— Contact tracing for household and close contacts

— Patients may not refuse treatment in some jurisdictions — civil commitment laws exist for non-adherent infectious TB

— Recognize and report occupational asthma, hypersensitivity pneumonitis, silicosis, asbestos exposure — workers' compensation eligibility; OSHA implications

— Document exposure history thoroughly

— Cough syncope counseling parallels syncope: advise driving cessation per state law and report if mandated; document the conversation

— Before prescribing low-dose morphine or codeine for refractory cough, document failure of all alternatives, check the state PDMP, screen for SUD risk, obtain informed consent about dependence, and arrange close follow-up

— Counsel that PPIs and ICS are being used diagnostically and therapeutically with expected 8–12 week trials and known long-term risks; document shared decision-making

— When a patient is referred to pulmonology, ENT, or GI, the PCP retains responsibility for medication reconciliation, follow-up of pending workup (CT findings, sputum cultures), and closing the loop on biopsy results — a common Step 3 safety theme

— Failure to follow up on an incidental pulmonary nodule on chronic cough CXR/CT is a recognized malpractice trigger; use a nodule-tracking system per Fleischner Society guidelines

Tuberculosis — mandatory reporting and public health:

Pertussis is also reportable; vaccinate close contacts and consider chemoprophylaxis (azithromycin) for high-risk exposures (infants, pregnant patients in 3rd trimester).

Occupational lung disease:

Driving safety:

Opioid stewardship:

Informed consent for empiric trials:

Transitions of care:

Health equity: chronic cough disproportionately under-evaluated in underserved populations; ensure equitable access to spirometry, CT, and specialist referral.

Board pearl: the most common patient-safety failure in chronic cough workup is a missed follow-up of an incidental lung nodule — always document and schedule the Fleischner-guided repeat imaging at the index visit.

High-Yield Associations and Rapid-Fire Clinical Facts

Big 3 in non-smoking adult with normal CXR: UACS, asthma, GERD — >90% of chronic cough.

≥2 causes coexist in ~25–50% of patients — add, don't switch, empiric therapies.

ACE inhibitor cough: bradykinin-mediated; 5–35%; resolves 1–4 weeks after stop; switch to ARB.

ARBs do NOT cause cough — clean substitute.

Methacholine challenge has high negative predictive value — used to rule OUT asthma.

NAEB: normal spirometry, negative methacholine, sputum eos >3%, high FeNO, ICS-responsive.

Cough-variant asthma: cough is the only symptom of asthma; PFTs often normal; methacholine positive.

GERD-cough: silent in 40–75%; PPI trial 8–12 weeks BID before declaring failure.

UACS empiric therapy of choice: 1st-gen antihistamine + decongestant (anticholinergic mechanism).

Lady Windermere syndrome: thin elderly women, MAC, RML/lingular bronchiectasis from voluntary cough suppression.

Ortner syndrome: left RLN palsy + cough from massive left atrium (mitral stenosis).

Arnold nerve reflex: ear canal stimulation → vagal cough; check ears.

Honey for cough >1 year only — never <1 year (botulism).

Benzonatate capsules: swallow whole — chewing fatal in children.

Codeine/tramadol: avoid in <12 years and breastfeeding (CYP2D6 ultra-rapid metabolizer deaths).

Lung cancer screening: LDCT yearly, ages 50–80, ≥20 pack-yr, current smoker or quit <15 years (USPSTF 2021).

Fleischner Society nodule rules guide CT follow-up.

Pertussis vaccination: Tdap each pregnancy 27–36 weeks.

Cough syncope = driving counseling per syncope rules.

Stress urinary incontinence affects 40–60% of women with chronic cough.

Gefapixant: P2X3 antagonist; dysgeusia common side effect.

Amiodarone, methotrexate, nitrofurantoin — drug-induced pulmonary toxicity classics.

Board pearl: if a stem mentions a smoker over 40 with change in chronic cough character ± hemoptysis or weight loss → CT chest, not another empiric trial — assume lung cancer until excluded.

Board Question Stem Patterns

Stem 1 — ACEi cough: "62-year-old man with HTN on lisinopril 6 months presents with dry cough for 10 weeks. Lungs clear, CXR normal." → Stop lisinopril, switch to ARB (losartan), reassess in 4 weeks. Distractor: empiric PPI, methacholine challenge.

Stem 2 — UACS: "34-year-old with throat clearing, postnasal drip sensation, cobblestoning of posterior pharynx, 12 weeks of cough, normal CXR." → Empiric 1st-gen antihistamine/decongestant trial × 2 weeks. Distractor: 2nd-gen antihistamine.

Stem 3 — Cough-variant asthma: "28-year-old with nocturnal cough, cough after laughing or cold air, normal spirometry, normal CXR." → Methacholine challenge (or empiric ICS trial). Distractor: chest CT.

Stem 4 — GERD-cough: "45-year-old obese man with chronic cough, worse postprandial and supine, no heartburn, normal CXR." → Lifestyle + PPI BID × 8–12 weeks. Distractor: bronchoscopy.

Stem 5 — NAEB: "Chronic cough, normal spirometry, negative methacholine, sputum eos 8%, FeNO 65 ppb." → Inhaled corticosteroid.

Stem 6 — Lung cancer red flag: "58-year-old, 40 pack-year smoker, 3 months of cough now with hemoptysis and 6-kg weight loss." → CT chest. Distractor: empiric PPI.

Stem 7 — IPF: "Dry cough, progressive dyspnea, Velcro crackles at bases, clubbing." → HRCT chest, refer pulmonology, consider antifibrotic.

Stem 8 — TB: "Recent immigrant, 3 months of cough, night sweats, weight loss, upper-lobe cavity on CXR." → Airborne isolation, 3 sputum AFB + NAAT, HIV test, report to health department.

Stem 9 — Pertussis: "Adult with 6 weeks of paroxysmal cough, post-tussive emesis." → Nasopharyngeal PCR, azithromycin, report; Tdap close contacts.

Stem 10 — Cardiogenic cough: "70-year-old with HTN, nocturnal cough, orthopnea, S3, elevated JVP." → BNP and echocardiogram, treat HF.

Stem 11 — Arnold nerve reflex: "Chronic cough, normal workup, cerumen impaction noted." → Cerumen removal.

Stem 12 — Refractory cough: "Big 3 fully treated, HRCT/spirometry/methacholine/pH study normal." → Speech-language pathology cough therapy ± gabapentin trial.

Step 3 management: when two answer choices both seem reasonable in cough stems, pick the one that completes the universal first steps (stop ACEi, CXR, smoking cessation) before any empiric trial.

One-Line Recap

The outpatient evaluation of chronic cough (>8 weeks) in an immunocompetent adult begins with stopping any ACE inhibitor, eliminating tobacco/exposures, and obtaining a CXR — followed by sequential, additive empiric trials for the "Big 3" (UACS → asthma → GERD), reserving HRCT, methacholine, FeNO, pH monitoring, and specialist referral for patients with red flags or failure of fully delivered empiric therapy.

Universal first steps: confirm duration ≥8 weeks, stop ACEi (reassess at 4 weeks), counsel smoking/exposure cessation, obtain CXR — no CT, bronchoscopy, or PFTs initially in uncomplicated cases.

Big 3 empiric algorithm (add, don't switch): UACS → 1st-gen antihistamine/decongestant × 2 weeks; Asthma → ICS × 4–8 weeks (methacholine if needed); GERD → lifestyle + PPI BID × 8–12 weeks; coexisting causes in 25–50%.

Red flags demanding early CT chest / specialist referral: hemoptysis, weight loss, fever, night sweats, focal lung findings, clubbing, progressive dyspnea, change in chronic cough character in a smoker >40, abnormal CXR — and remember LDCT lung cancer screening for eligible smokers.

Refractory cough (all Big 3 trials failed, normal advanced workup): label as cough hypersensitivity syndrome and use speech-language pathology cough-suppression therapy first, then trial gabapentin/pregabalin/low-dose morphine; emerging P2X3 antagonist gefapixant.

Board pearl: the three most-tested high-yield reflexes are — ACEi cough → stop and switch to ARB; smoker >40 with new/changed cough → CT chest, not empiric trial; chronic cough with normal spirometry but suspected asthma → methacholine challenge, which excludes asthma when negative.