Asthma Diagnosis

• Personal or family history of other atopic conditions (allergic rhinitis, eczema)
• Worsening of symptoms after exposure to common triggers (eg pollen, dust, exercise, viral infections, tobacco and e-cigarette smoke, Aspirin or nonsteroidal anti-inflammatory drug [NSAID], weather changes)
  • Bronchoconstriction induced by exercise usually occurs 5-10 minutes after completing the exercise

• Symptoms improved by appropriate antiasthmatic treatment

Asthma Symptom Control

• Consensus-based Global Initiative for Asthma (GINA) symptom control tool may be used to assess control of asthma
  • Useful together with risk assessment for treatment decision-making. Please see Risk Factors for Poor Asthma Outcomes Assessment for further information
• Asthma control may also be assessed using different validated measures such as asthma control test (ACT), childhood asthma control test (C-Act), asthma control questionnaire (ACQ), asthma therapy assessment questionnaire (ATAQ), or asthma control scoring system
  • May improve assessment of asthma control, provide reproducible objective measures, and allow better communication between physician and patients
  • ACT is a self-administered instrument that considers frequency of patient’s activity limitations, shortness of breath and night-time symptoms, use of rescue medication and rating of overall control of the disease within the past 4 weeks
    • The use of ACT for treatment response monitoring in a resource-limited setting has been found to be accurate and feasible
  • Sum of the factors considered will determine the level of patient’s asthma control and the management appropriate for the patient

• Because asthma symptoms are variable, physical exam may be normal
• If patient is examined during symptomatic period, they may present with dyspnea, hyperinflation, and expiratory wheezing
  • Wheezing may be absent (silent chest) especially with severe attacks

• Chronic asthma sufferers may have signs of hyperinflation with or without wheeze
• Allergic rhinitis or nasal polyposis may also be seen during examination of the nose

Measurements of Lung Function

• Assesses severity of airflow limitation, reversibility, and variability, and establishes the diagnosis of asthma
  • Documented excessive lung function variability AND documented expiratory airflow limitation defined as low forced expiratory volume in 1 second (FEV₁) and ratio of FEV₁ to forced vital capacity (FVC) confirm the diagnosis

• FEV₁ and peak expiratory flow (PEF) are decreased in obstructive airway diseases
• Spirometry and PEF measurements may be used to evaluate airflow limitation in patients ≥5 years old
• Predicted values of FEV₁, FVC and PEF based on age, gender and height may be used to base a judgment whether a value is normal or not 
  • Consider ethnic characteristics and extremes in age

Spirometry

• Recommended technique in determining airway limitation and reversibility, and confirming asthma
• FEV₁ and FVC are measured using a spirometer
  • A more reliable equipment for FEV₁ measurement as compared to PEF meters

• Other lung diseases can result in reduced FEV₁, better assessment of airflow limitation is by the ratio of FEV₁ to FVC
  • In the normal lung, FEV₁/FVC ratios are >75-80% in adults and >90% in children
  • FEV₁/FVC ratios <70% post-bronchodilator (or any value below the normal limit) are suggestive of airflow limitation

• >12% improvement in FEV₁ whether spontaneously, after inhalation of bronchodilator or after 4 weeks of anti-inflammatory treatment suggests a diagnosis of asthma
• Spirometry may also be used in the clinic to monitor the activity of asthma and is particularly helpful in assessing progress in patients with greatly compromised lung function

PEF

• PEF meters are important in the aid of diagnosis and the ensuing treatment of asthma
  • It is considered in patients who have a tendency to underperceive their symptoms (eg adolescents, have comorbidities with similar symptoms with asthma, elderly) or those likely to overperceive them (eg patients with anxiety)
• If spirometry is unavailable, PEF can confirm the presence of variable expiratory airflow limitation
• ≥20% improvement in PEF after inhalation of a bronchodilator suggests a diagnosis of asthma
• PEF measurements do not always correspond with other measurements of lung function in asthma
• PEF measurements should ideally be compared to the patient’s own previous best measurements
  • PEF measurements in children can be normal as airflow obstruction and gas trappings worsen and therefore, PEF can underestimate the degree of airflow obstruction

• Regular PEF measurements throughout the day or over week-month can aid in the assessment of asthma severity and response to treatment
  • Severity of asthma is also reflected in its variability especially across 24 hours

• Ideally, PEF should be measured first thing in the morning (when values are usually close to their lowest) and 12 hours apart in the evening (when values are usually at their highest)

Diurnal PEF

• Diurnal PEF variability is taken as the amplitude (difference between pre-bronchodilator morning value and post-bronchodilator value from the evening before) expressed as a percentage of the mean daily PEF value
• Another method is minimum morning pre-bronchodilator over 1 week expressed as percent of the recent best (Min%Max)
  • This method has been suggested to be the best PEF index of airway liability since it requires only once-a-day reading and correlates better than any other index with airway hyperresponsiveness

• An average daily diurnal variation in PEF >10% in adults and >13% in children is indicative of asthma
  • PEF testing should be done prior to treatment since PEF variability decreases with corticosteroid treatment as lung function improves

Bronchodilator (BD) Reversibility Test

• >12 % increase in FEV₁ and >200 mL from baseline, 10-15 minutes after 200-400 mcg Albuterol or its equivalent in adults, or >12% increase in FEV₁ in children, confirms the diagnosis of asthma
• Withholding administration of bronchodilators (≥4 hours for short-acting beta₂-agonists, 15 hours for long-acting beta₂-agonists) prior to test increases this test’s sensitivity

Other Tests

Exercise Challenge Test

• A decrease in FEV₁ by >10% and >200 mL from baseline in adults, and >12% predicted FEV₁ or PEF >15% in children

Bronchial Provocation Testing

• An alternative test to assess airway hyperresponsiveness
• A decrease from FEV₁ baseline of ≥20% with standard doses of methacholine (dose <4 mg/mL) or histamine, or ≥15% with standardized hyperventilation, hypertonic saline, or Mannitol challenge
  • Positive test with methacholine, histamine or Mannitol can occur in patients with allergic rhinitis, bronchiectasis, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF)

Allergy Tests

• Atopy, which is the most likely cause of respiratory symptoms in allergy-induced asthmatic patients, may be tested by skin prick testing or by measurement of specific immunoglobulin E (IgE) in serum
  • sIgE measurement may be preferred for patients who are uncooperative, with widespread skin disease, or if history suggests an anaphylaxis risk
  • May be used in asthma as a confirmatory test for patients with high probability for allergic asthma

Fractional Concentration of Exhaled Nitric Oxide (FENO) Measurement

• Increased in eosinophilic conditions (eg eosinophilic asthma, eosinophilic bronchitis, atopy, allergic rhinitis) and decreased in smokers, during bronchoconstriction, and early-onset allergic reactions
• A FeNO level of ≥40 parts per billion (ppb) in steroid-naive adults and ≥35 ppb in children is concluded positive
• Further studies are needed to prove the use of FeNO measurement in the diagnosis of asthma and to use this as a guide for adjusting asthma treatment
• Some studies that used FeNO-guided treatment strategies reported significant reduction in asthma exacerbation episodes and rate when compared to guideline-based strategies

Presence of Infrequent Symptoms

• The above tests may fail to support asthma diagnosis
• Surveillance and periodic re-evaluation should be maintained until the diagnostic situation is clearer
• Consider patient’s family history, age and asthma triggers before deciding on diagnostic and therapeutic course of action
• If in doubt, trial of treatment with short-acting beta₂-agonists as needed and inhaled corticosteroids assists in establishing the diagnosis of asthma especially if combined with PEF monitoring

• Assess patients for risk factors at diagnosis and periodically especially if with exacerbations
• Measure FEV₁ at the beginning of treatment and after 3-6 months of controller treatment

Risk Factors for Exacerbation

• Medications: Frequent short-acting beta₂-agonist, inadequate inhaled corticosteroids (not prescribed or poor adherence), beta-blockers, NSAIDs, incorrect inhaler technique
• Medical conditions: Obesity, gastroesophageal reflux disease, chronic rhinosinusitis, food allergy
• Exposures: Allergen, tobacco and e-cigarette smoke, air pollution, sulfites
• Lung function: Low FEV₁ (especially if <60% predicted), high BD reversibility
• Tests (in patients with type 2 inflammation): Blood eosinophils, elevated FeNO
• Psychological or socioeconomic problems
• Other independent risk factors: History of intubation or ICU admission for asthma, ≥1 severe exacerbation in the last 12 months

Risk Factors for Development of Persistent Airflow Limitation

• History: Preterm birth, low birth weight and greater infant weight gain, chronic mucus hypersecretion
• Medications: Lack of inhaled corticosteroids in treating patients who had severe exacerbation
• Exposures: Tobacco and e-cigarette smoke, occupational exposures
• Investigations: Low initial FEV₁, sputum or blood eosinophilia

Risk Factors for Medication Side Effects

• Systemic: Frequent oral corticosteroids, long-term use of high-dose inhaled corticosteroids, concomitant intake of P450 inhibitors
• Local: High-dose inhaled corticosteroids, poor inhaler technique

• Asthma exacerbations are events characterized by increased dyspnea, cough, wheezing, or chest tightness and progressive decrease in lung function
  
  • Described as having a reduction in expiratory airflow that is measured and monitored by lung function
  • May occur in patients previously diagnosed with asthma or as first presentation of asthma
• Goal of management is to immediately relieve airflow obstruction and hypoxemia, and to prevent further deterioration

Primary Care Management Assessment

Mild-Moderate Exacerbations

• Talks in phrases, prefers to sit, calm, RR increased, 100-120 bpm pulse rate, 90-95% O₂ saturation, PEF >50% predicted/personal best

Indications for Immediate Hospital Transfer (Severe Exacerbations)

•  RR >30/min, >120 bpm pulse rate, <90% O₂ saturation, PEF ≤50% predicted/best, accessory muscles in use, talks in words, hunched forward while sitting, agitated

Emergency Department Assessment

• Brief history and physical exam should be conducted while therapy is initiated

History

• Symptom severity
• Time of onset and cause
• Risks for possible asthma-related death, which necessitates closer medical supervision
  • History of asthma attack that needed intubation and mechanical ventilation
  • Hospitalized or emergency visit in the past year
  • Using oral/inhaled corticosteroid currently or recently stopped
  • Using >1 canister of inhaled rapid-acting beta₂-agonists monthly
  • With psychiatric or psychosocial problem
  • Noncompliant to management plan
  • Food allergy
• Any symptoms indicative of anaphylaxis
• All current medications including doses, devices, adherence pattern, changes in regimen and treatment response

Physical Exam

• Assess severity of exacerbation
• Mild-Moderate Exacerbations:
  • Prefers sitting, talks in phrases, no accessory muscles used, not agitated, RR increased, 100-120 bpm pulse rate, 100-120 bpm pulse rate, 90-95% O₂ saturation, PEF >50% predicted or best

• Severe Exacerbations:
  • RR >30/min, >120 bpm pulse rate, <90% O₂ saturation, PEF ≤50% predicted/best, accessory muscles in use, talks in words, hunched forward while sitting, agitated

• Examine for other factors that may complicate the condition (eg pneumonia, pneumothorax, atelectasis)

Functional Assessments

• PEF or FEV₁
  • If possible, obtain baseline prior to treatment without unduly delaying therapy, and until improvement is observed
• O₂ saturation
  • Preferably obtained by pulse oximetry
  • Helpful in children where lung function measurement is not reliable

Chest X-ray

• Requested only if there are suspected complicating factors, patient is for admission and not responding to treatment

Arterial Blood Gas

• Recommended in patients with PEF of <50% predicted, unresponsive to treatment, and signs of deterioration
  • Respiratory failure is indicated if results show PaO₂ <60 mmHg and normal or increased PaCO₂ (>45 mmHg)