Coughing is one of the most common reasons people seek medical attention, but when a cough lasts longer than 8 weeks, it's classified as chronic cough—a symptom that can be frustrating for patients and challenging for clinicians.
Understanding the differential diagnosis of chronic cough is crucial, and that’s where medical mnemonics like IA-SPICE come in handy. This clever acronym summarizes key causes that should always be considered during evaluation.
In this guide, we will explore each element of IA-SPICE, backed by clinical insights, underlying pathophysiology, diagnostic approaches, and management strategies.
What is Chronic Cough?
Chronic cough is defined as a cough lasting more than:
- 8 weeks in adults
- 4 weeks in children
It’s often dry or non-productive, but in some conditions, such as cystic fibrosis or post-infectious bronchitis, it can be productive (wet).
Chronic cough is not a disease in itself—it’s a symptom of an underlying condition.
Overview of the IA-SPICE Mnemonic
Let’s decode the mnemonic IA-SPICE, which stands for:
- I – Idiopathic
- A – Airway obstruction
- S – Sjögren’s and other inflammatory disorders
- P – Post-infectious causes
- I – Immunodeficiency
- C – Cystic fibrosis
- E – Esoterica (e.g., Young’s syndrome)
This structured approach ensures we cover a wide spectrum of respiratory, immunological, and systemic diseases.
I – Idiopathic Chronic Cough
Sometimes, all tests come back normal, and no definitive cause is found. This is termed Idiopathic chronic cough.
Possible Mechanisms:
- Hypersensitive cough reflex syndrome
- Neuropathic causes (e.g., vagal sensory neuropathy)
Clinical Features:
- Persistent dry cough
- Triggers: talking, cold air, perfumes
- No abnormal imaging or labs
Management:
- Neuromodulators: Gabapentin or amitriptyline
- Speech therapy
- Avoidance of known triggers
A – Airway Obstruction
This refers to structural or functional narrowing of airways.
Causes:
- Asthma
- Chronic obstructive pulmonary disease (COPD)
- Foreign body aspiration
- Tumors or mediastinal masses
- Tracheomalacia
Clinical Clues:
- Wheezing
- Dyspnea
- Stridor in upper airway obstruction
- Cough that worsens with exertion
Diagnosis:
- Chest X-ray, spirometry, CT thorax, bronchoscopy
Treatment:
- Bronchodilators
- Steroids
- Surgical intervention for tumors or foreign body
S – Sjögren’s Syndrome & Other Inflammatory Conditions
Chronic cough is frequently associated with autoimmune diseases, especially Sjögren’s syndrome.
Mechanisms:
- Xerotrachea (dry trachea)
- Associated interstitial lung disease (ILD)
Other Inflammatory Causes:
- Sarcoidosis
- Rheumatoid arthritis
- Systemic lupus erythematosus (SLE)
Symptoms:
- Dry eyes and mouth (Sjögren's)
- Joint pain
- Fatigue
Investigations:
- ANA, anti-Ro/La, HRCT chest
P – Post-Infectious Cough
Cough may linger for weeks after infection resolution, especially in viral or bacterial respiratory illnesses.
Common Triggers:
- Pertussis (whooping cough)
- Pneumonia
- COVID-19
- RSV and influenza viruses
Mechanism:
- Temporary airway hyperresponsiveness
- Mucosal irritation
Timeline:
- Cough persists for >3 weeks after infection
- Resolves gradually over 6–8 weeks
Treatment:
- Reassurance is key
- Occasionally, inhaled bronchodilators or steroids help
I – Immunodeficiency
Individuals with immune system dysfunction are more prone to persistent infections, leading to chronic cough.
Types:
- Primary immunodeficiencies (e.g., CVID)
- Secondary causes: HIV, chemotherapy, immunosuppressive therapy
Associated Infections:
- Recurrent bronchitis
- Pneumocystis pneumonia (PCP)
- CMV or EBV in immunocompromised hosts
Diagnostic Tests:
- Immunoglobulin levels
- HIV testing
- CD4 count
Management:
- Treat underlying immune issue
- Prophylactic antibiotics in severe cases
C – Cystic Fibrosis
Cystic Fibrosis (CF) is a genetic disorder affecting chloride transport, leading to thick mucus production.
Features:
- Persistent productive cough
- Recurrent lung infections
- Clubbing
- Pancreatic insufficiency
Diagnosis:
- Sweat chloride test
- Genetic testing (CFTR gene)
Management:
- Airway clearance therapy
- Mucolytics
- Antibiotics
- CFTR modulators
E – Esoterica (Young’s Syndrome)
This refers to rare or unusual causes of chronic cough.
Example: Young’s Syndrome
- Similar to CF: thick mucus and male infertility
- Normal sweat chloride test
- Cause: possibly environmental toxins or childhood infections
Other Esoteric Causes:
- Primary ciliary dyskinesia
- Bronchiolitis obliterans
- Tracheoesophageal fistula
Diagnostic Tools:
- High-resolution CT (HRCT)
- Bronchoscopy
- Ciliary beat frequency tests
Summary Table: IA-SPICE Mnemonic for Chronic Cough
| Mnemonic | Cause | Description | Key Clues |
|---|---|---|---|
| I | Idiopathic | No identifiable cause | Hypersensitive cough reflex |
| A | Airway obstruction | Narrowed airway due to asthma, tumor, COPD | Wheeze, dyspnea |
| S | Sjögren’s & other inflammation | Autoimmune-related dryness or ILD | Dry eyes, HRCT changes |
| P | Post-infectious | Cough persists post pneumonia or viral illness | History of recent infection |
| I | Immunodeficiency | Recurrent infections | HIV, CVID, neutropenia |
| C | Cystic Fibrosis | Thick mucus, genetic disorder | Clubbing, positive sweat test |
| E | Esoterica | Rare causes like Young’s syndrome | Infertility + thick sputum |
Differential Diagnosis: Expanding Beyond IA-SPICE
Although IA-SPICE is a brilliant framework, other major causes of chronic cough include:
- GERD (Gastroesophageal reflux)
- Postnasal drip
- ACE inhibitor use
- Smoking or vaping
- Habit cough in children
Consider the broader mnemonic: GAPES (GERD, Asthma, Postnasal drip, Eosinophilic bronchitis, Smoking)
Diagnostic Approach
A logical step-wise evaluation includes:
1. History & Physical Exam
Duration, triggers, sputum
2. Chest X-ray
- Rule out malignancy, pneumonia
3. Spirometry with bronchodilator response
4. Empirical trials
- PPI for GERD, antihistamines for PND
5. Advanced imaging
- HRCT, bronchoscopy if needed
FAQs
How long is a cough considered chronic?
A cough lasting more than 8 weeks in adults is chronic.
Can chronic cough be serious?
Yes. While often benign, it can also indicate lung cancer, tuberculosis, or interstitial lung disease.
What is the most common cause of chronic cough?
In non-smokers not on ACE inhibitors, the “big three” causes are:
- Asthma
- GERD
- Postnasal drip
What if cough persists despite treatment?
This is classified as refractory chronic cough. Referral to a pulmonologist and further testing is warranted.
🩺 Important Medical Concepts:
- Chronic Cough: Causes and Diagnostic Flow
- What Crosses the Placenta? (Mnemonic Based)
- TORCH Infections During Pregnancy
- APGAR Score: Newborn Evaluation Explained
- Hypocalcemia: Symptoms and ECG Signs
- Stroke: Types, Features, and Management
- Antibiotic Sensitivity and Resistance Patterns
- Clubbing of Fingers: Grades and Causes
- Laryngeal Cartilages: Anatomy Mnemonic
- Thyroid Gland Blood Supply Simplified
