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Asthma
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Here is a thorough overview of asthma symptoms and diagnosis, drawn from multiple authoritative medical textbooks:
Asthma: Symptoms & Diagnosis
Classic Symptoms
Asthma presents with four cardinal symptoms, all of which are intermittent and variable:
- Wheezing - the most recognized symptom
- Dyspnea (shortness of breath)
- Cough - sometimes the only symptom ("cough-variant asthma")
- Chest tightness / constriction - patients with asthma are more likely to describe this than patients with other cardiorespiratory diseases
Asthma should be in the differential diagnosis of any patient with intermittent respiratory symptoms. - Symptom to Diagnosis, 4th Ed.
Symptom Test Characteristics
From a community study of ~10,000 people, the predictive value of each symptom:
| Symptom | Sensitivity | Specificity | LR+ | LR- |
|---|---|---|---|---|
| Wheezing | 74.7% | 87.3% | 5.77 | 0.29 |
| Dyspnea at rest | ~47% | - | - | - |
Key note: asking "Do you cough during or after exercise?" achieves 90% specificity for asthma diagnosis using methacholine challenge as the gold standard. - Symptom to Diagnosis, 4th Ed.
When to Suspect Asthma (Triggering Clues)
Symptoms that occur or worsen with these triggers strongly support the diagnosis (per the National Asthma Education and Prevention Program):
- Exercise (airway cooling and drying)
- Viral infections (most common exacerbation cause)
- Allergens: animals, house dust mites, mold, pollen
- Irritants: smoke, perfumes, exhaust, chemicals
- Weather changes
- Night-time (due to decreased mucociliary clearance, airway cooling, low catecholamines)
- Laughing or hard crying
- Diurnal PEF variability > 20% between best and worst readings
Diagnostic Criteria
The three key diagnostic pillars (Washington Manual of Medical Therapeutics):
- Episodic symptoms of airflow obstruction
- Reversibility of airflow obstruction
- Exclusion of other likely diseases
Spirometry (Objective Test)
- FEV1 increase of ≥12% and an absolute increase of ≥200 mL after bronchodilator = confirms reversible airflow obstruction
- In the absence of reversibility at testing, a methacholine challenge test (airway hyperresponsiveness) can confirm the diagnosis
- Important: Lack of objective testing can lead to misdiagnosis in 30% of cases - Murray & Nadel's Textbook of Respiratory Medicine
Additional Tests
- Peak Expiratory Flow (PEF) monitoring: Serial measurements can show increased variability
- Adequate response to asthma treatment also supports the diagnosis
- Signs of atopy (eczema, allergic rhinitis, nasal polyps) frequently coexist with asthma
Severity Classification
| Classification | Symptoms | Lung Function (PEF) |
|---|---|---|
| Mild intermittent | <2 days/week; nighttime <2x/month | >80% predicted |
| Mild persistent | 2 days/week but <1x/day; nighttime >2x/month | >80% predicted |
| Moderate persistent | Daily symptoms; nighttime >weekly | 60-80% predicted |
| Severe persistent | Continuous symptoms; frequent nighttime | <60% predicted |
Differential Diagnosis
Conditions that can mimic asthma (especially in treatment-refractory patients):
- Upper airway: Vocal cord dysfunction, epiglottitis, obstructive sleep apnea, tumor
- Lower airway: COPD, cystic fibrosis, bronchiectasis, foreign body, ABPA
- Drug-induced: ACE inhibitors (cough), beta-blockers, aspirin (AERD)
- Other: GERD, sinusitis, CHF ("cardiac asthma"), eosinophilic pneumonia, hyperventilation/panic
Sources:
- Symptom to Diagnosis, 4th Ed. - core symptoms, triggers, test characteristics
- Washington Manual of Medical Therapeutics - diagnostic criteria, differential
- Murray & Nadel's Textbook of Respiratory Medicine - objective testing, spirometry
What are the treatment and management options for asthma?
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Here is a comprehensive overview of asthma treatment and management, synthesized from Harrison's Principles of Internal Medicine, Katzung's Pharmacology, and other authoritative textbooks.
Asthma: Treatment & Management
Core Goals of Therapy
All treatment aims at two parallel targets:
- Control of symptoms - minimize daily impairment (wheeze, dyspnea, cough, nighttime symptoms)
- Reduce future risk - prevent exacerbations, preserve lung function, avoid drug side effects
1. Non-Pharmacological (Trigger Reduction)
This is the foundation of management:
| Trigger | Intervention |
|---|---|
| Occupational exposures | Remove from environment (may fully resolve symptoms) |
| Allergens (pets, dust mites) | Remove pets; impermeable mattress/pillow covers |
| Cigarette smoke / cannabis | Cessation |
| Respiratory infections | Annual influenza vaccine, pneumococcal vaccines, COVID-19 & RSV vaccines |
| Allergen sensitization | Allergen immunotherapy (only in controlled, mild-moderate asthma; risk of anaphylaxis) |
2. Pharmacotherapy - Two Categories
A. Reliever (Rescue) Medications - Relax Smooth Muscle
Short-Acting Beta-2 Agonists (SABA) - e.g., albuterol/salbutamol
- First-line rescue therapy; rapid bronchodilation via cyclic AMP
- Regular (scheduled) use is discouraged - associated with tachyphylaxis and increased airway reactivity
- Used as-needed for acute symptoms or before exercise
Short-Acting Muscarinic Antagonists (SAMA) - e.g., ipratropium
- Less effective than SABAs in asthma; mainly adjunct in acute exacerbations
B. Controller (Maintenance) Medications - Target Inflammation
Inhaled Corticosteroids (ICS) - e.g., beclomethasone, budesonide, fluticasone
- The cornerstone of asthma control
- Reduce bronchial hyperreactivity; inhibit lymphocyte, eosinophil, and mast cell infiltration
- Do NOT relax smooth muscle directly
- Transformed treatment for all but mild intermittent asthma since the 1970s
- Katzung's Pharmacology, 16th Ed.
Long-Acting Beta-2 Agonists (LABA) - e.g., salmeterol, formoterol
- Never used as monotherapy in asthma (risk of severe exacerbations)
- Combined with ICS (ICS/LABA) for moderate-to-severe asthma
- Formoterol has rapid onset - can double as reliever (ICS/formoterol strategy)
Long-Acting Muscarinic Antagonists (LAMA) - e.g., tiotropium
- Add-on therapy when ICS +/- LABA is insufficient
- Tiotropium is as effective as adding a LABA to ICS in some patients
- Katzung's Pharmacology, 16th Ed.
Leukotriene Modifiers - montelukast (receptor antagonist), zileuton (synthesis inhibitor)
- Alternative to ICS for mild asthma when ICS is refused
- Particularly effective in aspirin-exacerbated respiratory disease (AERD) (~5-10% of asthmatics)
- FDA 2020 boxed warning for montelukast: serious neuropsychiatric events, suicidality, nightmares
Theophylline
- Phosphodiesterase inhibitor raising cAMP; older agent with narrow therapeutic window
- Rarely used now; reserved when other agents fail
3. Stepwise Therapy (GINA / NAEPP Guidelines, Ages 12+)
(Modified from Harrison's Principles of Internal Medicine, 22nd Ed., 2025)
| Step | Regular Controller | As-Needed Reliever |
|---|---|---|
| Step 1 (mild intermittent) | None | Low-dose ICS/formoterol or SABA |
| Step 2 (mild persistent) | Low-dose ICS OR LTRA | Low-dose ICS/formoterol or ICS+SABA |
| Step 3 (moderate persistent) | Low-dose ICS/formoterol | Low/medium-dose ICS/formoterol |
| Step 4 (moderate-severe) | Medium-dose ICS/formoterol | ICS/formoterol |
| Step 5 (severe/refractory) | High-dose ICS/LABA + LAMA | Biologics as add-on (see below) |
At every step: address triggers and comorbidities (rhinitis, GERD, obesity, anxiety).
4. Biologics (Targeted Monoclonal Antibody Therapy)
Used at Step 5 for severe, uncontrolled asthma:
| Drug | Target | Asthma Phenotype |
|---|---|---|
| Omalizumab | IgE | Allergic asthma |
| Mepolizumab | IL-5 | Eosinophilic asthma |
| Benralizumab | IL-5 receptor | Eosinophilic asthma |
| Reslizumab | IL-5 | Eosinophilic asthma |
| Dupilumab | IL-4 receptor (blocks IL-4 & IL-13) | Type 2 / eosinophilic asthma |
| Tezepelumab | TSLP | Broad (type 2 and non-type 2) |
Katzung's Basic and Clinical Pharmacology, 16th Ed.
5. Managing Acute Exacerbations
- Mild-moderate: Repeated SABA doses +/- early oral corticosteroids
- Severe exacerbations:
- Oral prednisone 40-60 mg/day with taper over 1-2 weeks
- Hospitalized patients: IV methylprednisolone 0.5-1 mg/kg every 6-12 hours until improved, then transition to oral
- Add ipratropium nebulization in the ED
- Consider IV magnesium sulfate in life-threatening attacks
- Key warning: Intensity of wheeze is an unreliable indicator of attack severity
6. Monitoring & Follow-up
- Peak Expiratory Flow (PEF) monitoring - daily variability >20% indicates poor control
- Spirometry every 1-2 years to monitor lung function decline
- Assess symptoms, reliever use frequency, exacerbation rate, and activity limitation at each visit
- Step therapy up if poorly controlled; step down once control is sustained for 3+ months
Sources:
- Harrison's Principles of Internal Medicine, 22nd Ed. (2025) - stepwise therapy, biologics, oral corticosteroids
- Katzung's Basic & Clinical Pharmacology, 16th Ed. - drug mechanisms, LAMA, leukotriene modifiers, monoclonal antibodies
- Washington Manual of Medical Therapeutics - exacerbation management
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