How do I diagnose and what is the first-line treatment for a new adult patient with suspected asthma?

Diagnosis and First-Line Treatment of Adult Asthma

Diagnostic Approach

Diagnose asthma when a patient presents with episodic respiratory symptoms (wheezing, dyspnea, cough, chest tightness) AND you demonstrate reversible airflow obstruction on spirometry—specifically an FEV₁ improvement ≥12% AND ≥200 mL after bronchodilator administration. 1, 2, 3

Key Diagnostic Steps

Confirm variable airflow obstruction through spirometry with bronchodilator testing:

• Perform baseline spirometry showing obstruction (FEV₁/FVC ratio reduced below normal for age: 85% for ages 8-19,80% for ages 20-39,75% for ages 40-59,70% for ages 60-80) 1
• Administer short-acting bronchodilator and repeat spirometry after 15 minutes 1
• Positive test: FEV₁ increases by ≥12% AND ≥200 mL from baseline in adults 1, 2

If initial spirometry is normal but clinical suspicion remains:

• Measure peak expiratory flow (PEF) twice daily for 2 weeks; variability >20% between readings suggests asthma 2
• Consider bronchial provocation testing with methacholine or exercise challenge (performed only by trained personnel for safety) 1
• Alternatively, initiate inhaled corticosteroid trial for 4 weeks; if FEV₁ improves by >12% and >200 mL post-treatment, this supports asthma diagnosis 1

Document symptom patterns that indicate asthma:

• Frequency of daytime symptoms (wheezing, shortness of breath, chest tightness, cough) 1
• Nighttime awakenings due to respiratory symptoms 1
• Activity limitation from respiratory symptoms 1, 2
• Symptom triggers: allergens, exercise, cold air, respiratory infections, NSAIDs 1
• Rescue inhaler use frequency 1, 2

Identify allergen sensitivities in all patients with persistent symptoms:

• Perform skin testing or specific IgE blood tests for perennial indoor allergens (house dust mite, cockroach, cat, dog, mold) 2
• This guides environmental control measures and identifies candidates for immunotherapy 1, 2

Critical Exclusions

Rule out alternative diagnoses before confirming asthma:

• COPD (check smoking history, obtain diffusing capacity if needed; COPD shows fixed obstruction without significant reversibility) 1
• Vocal cord dysfunction (look for inspiratory stridor, flattened inspiratory loop on spirometry, symptoms unresponsive to bronchodilators) 1
• Cardiac disease/heart failure (obtain chest X-ray, consider BNP if indicated) 1
• Gastroesophageal reflux disease (may coexist with asthma and worsen control) 1, 2

Classification of Severity for Treatment Initiation

Before starting therapy, classify severity using BOTH impairment and risk domains—assign the patient to the most severe category present in ANY feature. 1, 2

Impairment Domain (assess symptoms over past 2-4 weeks):

Severity	Daytime Symptoms	Night Awakenings	SABA Use	Activity Limitation	FEV₁
Intermittent	≤2 days/week	≤2×/month	≤2 days/week	None	>80% predicted
Mild Persistent	>2 days/week but not daily	3-4×/month	>2 days/week but not daily	Minor	>80% predicted
Moderate Persistent	Daily	>1×/week but not nightly	Daily	Some	60-80% predicted
Severe Persistent	Throughout day	≥4×/week	Several times/day	Extreme	<60% predicted

1, 2

Risk Domain:

• ≥2 exacerbations requiring oral corticosteroids in past year = higher severity regardless of impairment level 1, 2

First-Line Treatment by Severity

Intermittent Asthma (Step 1)

Prescribe as-needed low-dose ICS-formoterol (e.g., budesonide-formoterol) instead of SABA monotherapy—this reduces exacerbations compared to albuterol alone. 2

Mild Persistent Asthma (Step 2)

Initiate daily low-dose inhaled corticosteroid (ICS) as first-line controller therapy PLUS as-needed short-acting beta-agonist (SABA) for symptom relief. 1, 2

• ICS options: budesonide 180-400 mcg/day, fluticasone 88-264 mcg/day, or equivalent 1
• ICS improves asthma control more effectively than any other single long-term controller medication 1, 2
• Alternative (if ICS not tolerated): leukotriene receptor antagonist, though less effective 1

Moderate Persistent Asthma (Step 3)

Start combination low-to-medium dose ICS plus long-acting beta-agonist (LABA) as preferred therapy. 1, 2

• Preferred: ICS-LABA combination inhaler (e.g., fluticasone-salmeterol, budesonide-formoterol) 1
• This combination provides synergistic effects equal to or better than doubling ICS dose alone 2
• Alternative: medium-dose ICS alone, or low-dose ICS plus leukotriene receptor antagonist 1
• Never prescribe LABA as monotherapy—always combined with ICS 1, 3

Severe Persistent Asthma (Steps 4-6)

Prescribe high-dose ICS-LABA combination and refer to pulmonology/allergy specialist. 1

• Step 4: Medium-dose ICS-LABA 1
• Step 5: High-dose ICS-LABA, consider adding omalizumab if allergic asthma documented 1
• Step 6: High-dose ICS-LABA plus oral corticosteroid (minimize dose/duration) 1
• Specialist consultation recommended at Step 4 or higher 1, 2

Essential Initial Management Components

Teach and verify proper inhaler technique at the first visit—incorrect technique is a common cause of treatment failure. 2

Provide a written asthma action plan that includes:

• Daily controller medication regimen 1, 2
• When to use rescue inhaler 2
• How to recognize worsening (PEF <80% personal best, increased symptoms, increased rescue use) 2
• When to increase treatment or seek urgent care 1, 2

Identify and address environmental triggers:

• Eliminate tobacco smoke exposure completely 2
• Reduce allergen exposure based on positive skin/IgE testing (dust mite covers, remove pets if sensitized, control mold/cockroach) 2
• Avoid occupational sensitizers if identified 1

Screen for and treat comorbidities that worsen asthma control:

• Allergic rhinitis/chronic rhinosinusitis (treat with intranasal corticosteroids) 2
• Gastroesophageal reflux disease 1, 2
• Obesity 2
• Obstructive sleep apnea 4
• Anxiety/depression 2

Administer annual influenza vaccination to all patients with persistent asthma. 2

Monitoring and Follow-Up

Schedule follow-up within 2-4 weeks after initiating therapy to assess response:

• Repeat spirometry to document improvement 2
• Assess symptom control using validated tools (Asthma Control Test [ACT] score ≥20 = well-controlled) 1, 2
• Verify inhaler technique again 2

Well-controlled asthma is defined as:

• Daytime symptoms ≤2 days/week 1, 2
• No nighttime awakenings 1, 2
• SABA use ≤2 days/week 1, 2
• No activity limitation 1, 2
• FEV₁ or PEF ≥80% predicted or personal best 1, 2
• No exacerbations requiring oral corticosteroids 1

If not well-controlled after 4 weeks, step up therapy before considering alternative diagnoses or poor adherence. 1, 2

Common Pitfalls to Avoid

• Do not rely on symptoms alone—always obtain spirometry to confirm diagnosis; clinical history and exam are unreliable for excluding other diagnoses 1, 5
• Do not use peak flow meters for diagnosis—they have wide variability and are designed for monitoring, not diagnosis 1
• Do not prescribe LABA without ICS—LABA monotherapy increases mortality risk 1, 3
• Do not assume all wheezing is asthma—always consider vocal cord dysfunction, heart failure, COPD, and foreign body 1
• Do not overlook poor inhaler technique—this is the most common correctable cause of treatment failure 2, 6