Lucan · Conditions

Adult asthma

Australian guidance: Australian Asthma Handbook v3.0 (NACA, 2025)

1. Definition and epidemiology

Asthma is a chronic inflammatory lung condition defined as the combination of variable respiratory symptoms (wheeze, breathlessness, chest tightness, cough) and variable expiratory airflow limitation. Approximately 2.8 million Australians (11% of the population) are diagnosed with asthma, making it one of the most prevalent chronic conditions in the country. Adult-onset asthma can present at any age and must be actively considered in older adults who lack a childhood diagnosis.

2. Pathophysiology

The core lesion in asthma is chronic airway inflammation, predominantly driven by type 2 immune responses. Allergen or irritant exposure activates mast cells and Th2 lymphocytes, producing interleukin (IL)-4, IL-5, and IL-13. IL-5 drives eosinophil recruitment and survival; IL-13 promotes mucous gland hyperplasia and goblet cell metaplasia. The resulting airway wall changes include subepithelial fibrosis (basement membrane thickening), smooth muscle hypertrophy, and mucosal oedema. Bronchoconstriction arises from smooth muscle hyperresponsiveness to a range of stimuli including cold air, exercise, allergens, and viral infections. Recurring inflammation over years can produce fixed airflow obstruction through airway remodelling, even in patients who were previously well controlled. A minority of patients exhibit non-type-2 (neutrophilic or paucigranulocytic) phenotypes that respond poorly to inhaled corticosteroids alone (Robbins Ch 15 The Lung).

3. Clinical presentation and diagnostic criteria

The hallmark history is recurrent or persistent wheeze, breathlessness, chest tightness, and cough that vary in frequency and severity over time. Symptoms that worsen with exercise and persist or worsen after stopping activity are particularly suggestive. Nocturnal symptoms and worsening after viral infections, cold air, or allergen exposure are characteristic patterns. On examination, widespread expiratory wheeze on auscultation supports the diagnosis but is neither sensitive nor specific; the examination is often entirely normal between exacerbations. A silent chest in a distressed patient signals life-threatening bronchoconstriction. Diagnosis requires both a typical symptom history and objective demonstration of variable expiratory airflow limitation or airway inflammation; history alone is insufficient.

4. Investigations and AU-specific cutoffs

Spirometry with bronchodilator responsiveness testing is the cornerstone investigation. A positive bronchodilator response is defined as an increase in FEV1 of at least 200 mL and at least 12% from the pre-bronchodilator value, measured 10 to 15 minutes after administering salbutamol. An increase exceeding 400 mL provides strong support for asthma. Fractional exhaled nitric oxide (FeNO) should be measured concurrently when spirometry is performed in an accredited laboratory; a value of 40 ppb or above supports the diagnosis in the appropriate clinical context (sensitivity 0.61, specificity 0.82 in adults). Where spirometry is not immediately available, a peak expiratory flow diary maintained for two to four weeks is an acceptable interim measure; mean diurnal variability greater than 10% supports the diagnosis. If spirometry and FeNO are inconclusive but asthma remains suspected, referral for bronchial provocation testing (methacholine, mannitol, or exercise challenge) is appropriate, noting that it is contraindicated when FEV1 is below 60% predicted or during pregnancy. Chest X-ray is not required for diagnosis but is indicated when an alternative or comorbid diagnosis needs to be excluded.

5. Management

AU guideline management follows a stepped, patient-centred framework with the goal of minimising symptoms, preventing exacerbations, and preserving lung function. All treatment levels must include an inhaled corticosteroid (ICS); as-needed short-acting beta-2 agonist (SABA) alone is not acceptable at any level of symptom severity. The recommended first-line approach after diagnosis is low-dose budesonide-formoterol taken as needed (anti-inflammatory reliever, or AIR, therapy), which is equally or more effective than daily ICS at preventing severe exacerbations and delivers a lower cumulative ICS dose. Maintenance treatment with low-dose ICS plus salbutamol as needed is the recommended alternative when AIR therapy is not preferred or accessible. Follow-up should be arranged within two to three months of initiation to reassess symptom control, adherence, and inhaler technique. Stepping up to low-dose or medium-dose maintenance and reliever therapy (MART) is indicated when AIR therapy is insufficient; MART uses a single ICS-formoterol inhaler for both daily maintenance and as-needed relief. Before stepping up treatment, poor adherence, incorrect inhaler technique, and ongoing trigger exposure should be addressed. A personal written asthma action plan is mandatory for all patients. For acute exacerbations in the primary care setting, salbutamol 4 to 12 actuations via pressurised metered dose inhaler (pMDI) plus spacer every 20 minutes for the first hour is first-line, with systemic corticosteroids (prednisone or prednisolone 37.5 to 50 mg orally each morning for 5 to 10 days) started regardless of severity unless contraindicated. Transfer to emergency care is required if the patient cannot speak in whole sentences or has SpO2 at or below 94%.

6. Pharmacology and AU PBS notes

Level 1 (AIR therapy). Budesonide-formoterol (Symbicort Turbuhaler or TGA-approved equivalents) taken as needed. Only certain devices are TGA-approved for AIR use; the prescriber must specify the correct inhaler. As-needed SABA alone (salbutamol, such as Ventolin) is not PBS-subsidised as the sole asthma therapy under current guidelines and is associated with increased exacerbation and death risk. Level 2 to 3 (MART). Maintenance plus as-needed low or medium-dose budesonide-formoterol. MART is not PBS-reimbursed as initial treatment for asthma; prescribers must meet relevant PBS criteria for stepping up. Level 4 (severe asthma). High-dose ICS-LABA (long-acting beta-2 agonist) combinations, with consideration of long-acting muscarinic antagonist (LAMA) add-on (tiotropium, PBS-listed for severe uncontrolled asthma) or biologic therapy. Monoclonal antibodies subsidised on PBS for eligible patients include omalizumab (anti-IgE, for allergic asthma with serum IgE 30 to 1500 IU/mL and weight-adjusted dosing), mepolizumab, benralizumab, and dupilumab (anti-IL-4/IL-13), each requiring specialist initiation and defined eosinophil or FeNO thresholds. ICS local adverse effects (oral candidiasis, dysphonia) are reduced by using a valved spacer with pMDI devices and rinsing the mouth after each dose.

7. Complications and monitoring

The main complications of poorly controlled asthma include repeated severe exacerbations requiring oral corticosteroids, fixed airflow obstruction from airway remodelling, and asthma-related death. Cumulative oral corticosteroid exposure above 1000 mg prednisolone significantly increases risk of type 2 diabetes mellitus, osteoporosis, cardiovascular and cerebrovascular disease, cataracts, and adrenal insufficiency; minimising oral corticosteroid use through optimised inhaled therapy is a core management priority. Dispensing of three or more 200-dose SABA canisters per year signals high exacerbation risk and warrants urgent review; twelve or more canisters per year is associated with asthma death. Monitoring should include reassessment of symptom control and lung function every one to three months when stepping up, and every one to three months for four to six weeks after each step-down to confirm stability. Blood eosinophil count should be checked when control remains poor on medium-dose ICS-LABA; a count of 150 cells per microlitre or above signals refractory type 2 inflammation, and a count of 1500 cells per microlitre or above warrants urgent specialist review. Asthma in pregnancy requires the same treatment targets as in non-pregnant adults, with no step-down during pregnancy unless doses are excessive.

Written for Australian practice and grounded in the guidance named above. Study material only — not medical advice. Always check against current guidelines.