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Asthma severity classification is the systematic assessment of asthma control and underlying disease intensity, which directly determines the appropriate step of pharmacotherapy. The Global Initiative for Asthma (GINA) 2023 guidelines classify asthma into four severity categories based on symptom frequency, nocturnal symptoms, activity limitation, lung function (FEV1 and FEV1/FVC), and exacerbation history — assessed retrospectively after a patient has been on appropriate treatment for at least 2–3 months: Intermittent (symptoms ≤2 days/week, no interference with activity, FEV1 ≥80% predicted, normal FEV1/FVC, 0–1 exacerbation per year), Mild Persistent (symptoms >2 days/week but not daily, minor interference, FEV1 ≥80%, normal FEV1/FVC, ≥2 exacerbations/year), Moderate Persistent (daily symptoms, some limitation, FEV1 60–79% predicted, FEV1/FVC reduced 5%, ≥2 exacerbations/year), and Severe Persistent (continuous symptoms throughout the day, frequent nocturnal symptoms, extreme limitation, FEV1 <60% predicted, FEV1/FVC reduced >5%, ≥2 exacerbations/year). These severity categories map directly to GINA Step 1–5 pharmacotherapy: Step 1 (as-needed low-dose ICS-formoterol for intermittent asthma), Step 2 (daily low-dose ICS or as-needed ICS-formoterol for mild persistent), Step 3 (low-dose ICS-LABA or medium ICS for moderate persistent), Step 4 (medium/high ICS-LABA for severe persistent), and Step 5 (add-on therapy: tiotropium, anti-IgE/IL-5/IL-4Ra biologics, or low-dose OCS). Spirometry with bronchodilator reversibility is essential: a post-BD increase in FEV1 ≥12% and ≥200 mL confirms bronchodilator reversibility and supports the asthma diagnosis. Peak flow monitoring and asthma control questionnaires (ACQ, AQLQ) complement severity classification.
GINA Severity: Intermittent (≤2d/wk, FEV1≥80%), Mild Persistent (>2d/wk, FEV1≥80%), Moderate Persistent (daily, FEV1 60–79%), Severe Persistent (continuous, FEV1<60%); Step 1–5 therapy
- 1Assess daytime symptom frequency: ≤2 days/week = intermittent; >2 days/week but not daily = mild persistent; daily = moderate persistent; continuous throughout day = severe persistent.
- 2Assess nocturnal symptoms: none = intermittent; ≤4 nights/month = mild persistent; >1 night/week = moderate persistent; frequent (most nights) = severe persistent.
- 3Assess activity limitation: none = intermittent; minor limitation = mild persistent; some limitation = moderate persistent; extreme limitation = severe persistent.
- 4Perform spirometry: FEV1 ≥80% + normal FEV1/FVC = intermittent or mild; FEV1 60–79% + reduced FEV1/FVC = moderate; FEV1 <60% + markedly reduced FEV1/FVC = severe.
- 5Count exacerbations: 0–1/year = intermittent; ≥2/year in mild–severe (any exacerbation requiring OCS, ED visit, or hospitalisation).
- 6Map severity to GINA Step: Step 1 (intermittent), Step 2 (mild persistent), Step 3 (moderate persistent), Step 4–5 (severe persistent).
- 7Initiate step-appropriate therapy; reassess in 4–8 weeks; step up if uncontrolled, step down if controlled for ≥3 months.
GINA 2023 no longer recommends SABA-alone as Step 1 due to risk of severe exacerbation without ICS
Classic intermittent asthma with normal lung function. GINA now recommends as-needed ICS-formoterol as preferred Step 1 to reduce exacerbation risk.
Also consider spirometry reversibility testing and allergen sensitisation screen
Daily symptoms with reduced FEV1 and exacerbation history places this patient at Step 3. Low-dose ICS-LABA combination is the most effective Step 3 regimen.
Biologics: mepolizumab/benralizumab (type 2 eosinophilic); dupilumab (type 2 broad); omalizumab (allergic, IgE-mediated)
A patient on Step 4 who remains uncontrolled with eosinophilic phenotype and frequent exacerbations is a candidate for anti-IL-5 biologic therapy at Step 5.
Do not step down during high-risk periods (viral URTI season, pollen season in allergic patients)
Sustained control for 6 months warrants step-down to reduce medication burden and side effects while maintaining asthma control.
Initiating the correct step of therapy at first asthma diagnosis based on severity classification.. This application is commonly used by professionals who need precise quantitative analysis to support decision-making, budgeting, and strategic planning in their respective fields
Step-up decision-making when a patient reports uncontrolled symptoms at a medication review appointment.. Industry practitioners rely on this calculation to benchmark performance, compare alternatives, and ensure compliance with established standards and regulatory requirements
Biologic therapy eligibility assessment: confirming Step 4–5 severity and eosinophilic/allergic phenotype for funding approval.. Academic researchers and students use this computation to validate theoretical models, complete coursework assignments, and develop deeper understanding of the underlying mathematical principles
Occupational health: classifying asthma severity to guide fitness-for-work assessments and workplace exposure management.. Financial analysts and planners incorporate this calculation into their workflow to produce accurate forecasts, evaluate risk scenarios, and present data-driven recommendations to stakeholders
Paediatric asthma clinics: tracking severity classification over time to guide decisions about stepping down as lung growth continues.. This application is commonly used by professionals who need precise quantitative analysis to support decision-making, budgeting, and strategic planning in their respective fields
Aspirin-Exacerbated Respiratory Disease (AERD)
AERD (Samter's triad) is the combination of asthma, chronic rhinosinusitis with nasal polyps, and aspirin/NSAID hypersensitivity, affecting approximately 10–20% of adults with severe asthma. These patients need to avoid all NSAIDs and aspirin. Aspirin desensitisation under medical supervision can reduce polyp recurrence and improve asthma control. Anti-IL-5 and anti-IL-4/13 biologics are highly effective in AERD.
Occupational Asthma
Occupational asthma (OA) is triggered by workplace sensitisers (high molecular weight: flour, latex, animal proteins; low molecular weight: isocyanates, reactive dyes, formaldehyde). OA accounts for 10–15% of adult-onset asthma. Diagnosis requires confirmation that symptoms are work-related (serial PEF monitoring at/away from work, specific inhalation challenge). Complete removal from exposure is the most effective treatment — ongoing exposure worsens prognosis and leads to persistent asthma even after cessation.
Exercise-Induced Bronchoconstriction (EIB)
EIB occurs in approximately 90% of asthma patients and up to 40% of elite athletes without known asthma. It is caused by airway cooling and drying during high-flow breathing during exercise. Diagnosis: ≥10% fall in FEV1 after standardised exercise challenge. Treatment: pre-exercise ICS-formoterol or SABA; montelukast can be added for EIB in athletes. In athletes, all asthma medications must be checked against anti-doping regulations.
Difficult-to-Treat vs Severe Asthma
Before diagnosing truly severe asthma (requiring Step 4–5 biologics), all 'difficult-to-treat' causes must be excluded: poor inhaler technique (up to 40% of patients use inhalers incorrectly), poor adherence to treatment, uncontrolled comorbidities (allergic rhinitis, GORD, obesity, OSA, vocal cord dysfunction), ongoing smoking, or incorrect asthma diagnosis (COPD, cardiac dyspnoea, vocal cord dysfunction misdiagnosed as asthma). A structured severe asthma assessment by a specialist should precede biologic prescription.
| Severity | Daytime Symptoms | FEV1 % Predicted | GINA Step | Preferred Controller |
|---|---|---|---|---|
| Intermittent | ≤2 days/week | ≥80% | Step 1 | As-needed low-dose ICS-formoterol |
| Mild Persistent | >2 days/week, not daily | ≥80% | Step 2 | Low-dose ICS or as-needed ICS-formoterol |
| Moderate Persistent | Daily | 60–79% | Step 3 | Low-dose ICS-LABA |
| Severe Persistent | Continuous | <60% | Steps 4–5 | Medium/high ICS-LABA ± biologic |
What is the difference between asthma severity and asthma control?
Asthma severity reflects the underlying intensity of the disease process and is assessed retrospectively based on the step of treatment required to achieve control. Asthma control refers to the degree to which the manifestations of asthma are reduced or removed by treatment, assessed at each visit as well-controlled, partly controlled, or uncontrolled. A patient with severe asthma requiring Steps 4–5 may achieve good control on that treatment. Control is assessed at each visit; severity is reassessed after months of treatment.
What is the GINA Track 1 vs Track 2 approach?
GINA 2023 presents two preferred treatment tracks. Track 1 (preferred): uses low-dose ICS-formoterol as both the daily maintenance AND as-needed reliever across all steps — this 'MART' (Maintenance And Reliever Therapy) approach with budesonide-formoterol reduces severe exacerbations more effectively than SABA-based regimens. Track 2 (alternative): uses SABA as the as-needed reliever alongside ICS or ICS-LABA maintenance. Track 1 is now preferred at all steps due to superior exacerbation prevention.
When should biologics be considered for asthma?
Biologics are indicated for Step 5 severe asthma that is uncontrolled despite optimised Step 4 therapy (high-dose ICS-LABA) after confirming: good inhaler technique, adherence, no modifiable risk factors (smoking cessation, allergen avoidance), and no complicating diagnoses (vocal cord dysfunction, ABPA). Biologic selection is driven by the asthma phenotype: anti-IgE (omalizumab) for allergic asthma; anti-IL-5 (mepolizumab, reslizumab) or anti-IL-5R (benralizumab) for eosinophilic asthma (eosinophils ≥300); anti-IL-4/13R (dupilumab) for type 2 asthma with ≥300 eosinophils or FeNO ≥25.
What is a severe acute asthma attack and how is it managed?
A severe acute asthma attack is characterised by: SpO2 <92%, PEF 33–50% best/predicted, inability to complete sentences, HR >120 bpm, RR >25/min, or use of accessory muscles. Treatment: high-flow oxygen to SpO2 94–98%, nebulised salbutamol 2.5–5 mg every 20 minutes, ipratropium bromide 0.5 mg nebulised, IV or oral prednisolone 40–50 mg, and IV magnesium sulphate 1.2–2 g if no response. Life-threatening features (SpO2 <92%, silent chest, PEF <33%, confusion, cyanosis) require immediate senior review and may need NIV or invasive ventilation.
What is FeNO and how does it help in asthma?
Fractional exhaled nitric oxide (FeNO) is a non-invasive marker of eosinophilic airway inflammation. FeNO above 40–50 ppb supports a diagnosis of eosinophilic asthma, predicts response to ICS, and identifies candidates for anti-IL-4/13 biologic therapy (dupilumab). FeNO below 25 ppb suggests non-eosinophilic asthma where increasing ICS dose is unlikely to help. FeNO is available in specialist asthma clinics and is recommended in GINA 2023 for phenotyping and biologic selection.
What triggers asthma and how can they be avoided?
Common asthma triggers include: allergens (house dust mite, pet dander, pollen, mould), respiratory infections (viral URTI — the most common exacerbation trigger in both children and adults), exercise, cold air, air pollutants (NO2, particulate matter), cigarette smoke (active and passive), aspirin/NSAIDs (in aspirin-exacerbated respiratory disease, AERD), beta-blockers, occupational exposures (flour dust, isocyanates, latex), and emotional stress. Trigger identification and avoidance are core components of asthma management.
How is childhood asthma different from adult asthma?
In children, asthma diagnosis below age 5 is more challenging because wheeze is common from viral infections ('preschool wheeze'). The diagnosis of true persistent asthma in young children requires recurrent wheezing, response to bronchodilator, family history, and eczema/allergic rhinitis. Children with asthma more often have allergic triggers (atopic asthma). A proportion of children 'outgrow' asthma at puberty, though many relapse in adulthood. ICS remain the cornerstone of controller therapy in paediatric asthma.
What is the role of peak flow monitoring in asthma?
Peak expiratory flow (PEF) monitoring provides objective, real-time measurement of large airway obstruction. A PEF diary (twice daily over 2–4 weeks) with >20% diurnal variability supports the asthma diagnosis. In acute attacks, PEF classifies severity and guides treatment decisions: PEF ≥75% = mild; 50–75% = moderate; 33–50% = severe; <33% = near-fatal. Personal best PEF (rather than predicted PEF) is more accurate for monitoring individual asthma control.
プロのヒント
Before considering any step-up or biologic prescription, complete the 'asthma five-step check': (1) Confirm the diagnosis — is it really asthma? (2) Check inhaler technique in person or via video. (3) Confirm adherence — pharmacy refill records can be revealing. (4) Identify and address modifiable risk factors (smoking, allergen exposure, obesity). (5) Screen for and treat comorbidities (rhinitis, GORD, OSA). Only after these are optimised should pharmacological stepping-up be considered.
ご存知でしたか？
Asthma has afflicted some of history's most accomplished individuals: John F. Kennedy had severe asthma throughout his life and received daily corticosteroid injections during his presidency. Ludwig van Beethoven had asthma alongside his famous deafness. Charles Dickens was asthmatic and famously described children with asthma in his novels. Marcel Proust's severe asthma played a direct role in his famous years of semi-reclusive writing that produced 'In Search of Lost Time.'
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