Asma Bronkiale Dewasa

01Pathophysiology

Asthma is fundamentally a disease of chronic airway inflammation with a heterogeneous immunologic basis. The Asma Dewasa PDPI 2021 emphasizes that the immunopathogenesis follows a Th2-dominant pathway in the majority of patients, though non-Th2 phenotypes exist.

When a genetically susceptible individual encounters an aeroallergen, dendritic cells (antigen-presenting cells residing in the airway epithelium) capture and process the allergen, then present it to naive T-helper cells in regional lymph nodes. This drives differentiation toward the Th2 subset, which produces the key cytokines IL-4, IL-5, and IL-13. IL-4 promotes IgE class-switching in B-lymphocytes, generating allergen-specific IgE that coats mast cell surfaces via high-affinity FcεRI receptors. Upon re-exposure, allergen cross-links surface-bound IgE, triggering mast cell degranulation and release of histamine, prostaglandins, and leukotrienes. This is the early-phase response (minutes), producing acute bronchoconstriction, mucosal edema, and mucus hypersecretion. IL-5 is the principal cytokine responsible for eosinophil recruitment, activation, and survival in the airways. Eosinophil-derived mediators (major basic protein, eosinophil cationic protein) damage epithelial cells and perpetuate inflammation. This late-phase response (4-8 hours) sustains and amplifies symptoms. IL-13 acts on airway smooth muscle and goblet cells, driving mucus overproduction and bronchial hyperreactivity.

This is exactly why the patient presents the way they do: the bronchoconstriction causes wheezing and dyspnea, mucus plugging causes cough and chest tightness, and the variable, reversible nature of smooth muscle contraction explains the episodic pattern with symptom-free intervals. The reason symptoms are worse at night relates to circadian variation in cortisol levels, vagal tone, and airway caliber.

Over time, chronic inflammation leads to airway remodeling: subepithelial fibrosis, smooth muscle hypertrophy, goblet cell hyperplasia, angiogenesis, and thickening of the basement membrane. The Asma Dewasa PDPI 2021 identifies this as the mechanism behind the "asthma with fixed airway obstruction" phenotype, where patients develop irreversible obstruction despite treatment. This remodeling is why early initiation of inhaled corticosteroids (ICS) is critical: ICS targets the inflammatory cascade upstream, reducing eosinophilic infiltration and preventing structural damage.

The guideline also highlights two non-Th2 endotypes of importance. Non-allergic asthma features neutrophilic or paucigranulocytic sputum and responds poorly to ICS. Late-onset asthma, more common in women, tends to lack atopic features and often requires higher ICS doses. Understanding these endotypes is critical because the vignette may describe a patient with asthma that is "refractory to ICS," pointing toward a non-eosinophilic or non-Th2 phenotype.

02Classification and Clinical Manifestation

Asthma Frequency Classification

Acute Exacerbation Severity

Asthma Control Level

Assessed over the preceding 4 weeks using four questions:

Frequency is determined before treatment in a treatment-naive patient and classifies the disease itself. Control is assessed on treatment at every visit and guides step-up or step-down decisions. Exam questions that present a patient already on therapy are testing your understanding of control level, not severity.

Asthma Phenotypes

03Diagnostic Workup

The best initial test is spirometry because it provides objective evidence of airflow obstruction and, critically, its reversibility. The Asma Dewasa PDPI 2021 explicitly states that spirometry ($FE{V}_{1}FEV\_1$) is preferred over PEF. You are looking for an obstructive pattern () followed by a bronchodilator reversibility test: administer salbutamol 400 mcg (or 2 x 2 puffs) via metered-dose inhaler, then repeat spirometry after 15-20 minutes. An increase in $FE{V}_1\ge 12FEV\_1\; \backslash geq\; 12\%$ AND $\ge 200mL\backslash geq\; 200\backslash \; mL$ from baseline confirms reversible airflow obstruction, which is the hallmark of asthma. If spirometry is not available, PEF can be substituted, and a PEF improvement $\ge 20\backslash geq\; 20\%$ after bronchodilator has equivalent diagnostic weight.

When a patient presents with classic symptoms but spirometry is normal (common because asthma is episodic), the next step is a bronchial provocation test using methacholine, histamine, exercise challenge, eucapnic voluntary hyperventilation, or inhaled mannitol. This test has excellent sensitivity, meaning a negative result in a patient not on ICS helps exclude asthma. However, its specificity is limited because conditions like allergic rhinitis, cystic fibrosis, bronchopulmonary dysplasia, and COPD can also produce a positive result.

FeNO is an increasingly used adjunct. A FeNO level > 50 ppb in a nonsmoking patient with nonspecific respiratory symptoms correlates with eosinophilic airway inflammation and predicts a good short-term response to ICS. However, the Asma Dewasa PDPI 2021 states that FeNO is not currently recommended as a standalone decision tool for initiating ICS, because long-term safety data on withholding ICS based on low FeNO are insufficient.

Allergy testing (skin prick test or serum IgE) supports the diagnosis by confirming atopic status, but the guideline emphasizes that a positive test alone does not prove that the identified allergen is causing the symptoms. The association between allergen exposure and symptom onset must be confirmed by clinical history.

Chest X-ray in stable asthma is typically normal or shows hyperinflation and primarily serves to exclude alternative diagnoses.

04Management & Treatment

Stable Asthma

The Asma Dewasa PDPI 2021 adopts the GINA 2020 paradigm shift that is arguably the most testable concept in modern asthma management: SABA-only treatment is no longer recommended for adults and adolescents.

This is a direct result of evidence linking SABA overuse ($\ge \backslash geq$ 3 canisters/year, or an average of $\ge \backslash geq$ 1.5 inhalations/day) with increased exacerbation risk, emergency department visits, hospitalizations, and mortality. Using $\ge \backslash geq$ 12 canisters/year (1 canister/month) increases mortality risk.

At Step 1, the recommended reliever is low-dose ICS-formoterol as needed. Formoterol is unique among LABAs because it has a rapid onset of action (comparable to salbutamol) AND a long duration, making it suitable as both a reliever and controller. This as-needed ICS exposure ensures even patients with very infrequent symptoms receive anti-inflammatory therapy whenever they use a bronchodilator.

At Step 2, the preferred approach is either daily low-dose ICS with SABA as needed, or low-dose ICS-formoterol as needed. The alternative is a leukotriene receptor antagonist (LTRA), but the guideline explicitly notes LTRA is less effective than low-dose ICS (Evidence Level A vs B).

At Step 3, low-dose ICS-LABA becomes the preferred controller. The guideline highlights ICS-formoterol used as both maintenance and reliever therapy (MART strategy), with a maximum formoterol dose of 72 mcg/day. For patients with $\ge \backslash geq$ 1 exacerbation in the past year, MART significantly reduces exacerbation rates.

At Step 4, the key addition is tiotropium (long-acting muscarinic antagonist/LAMA) as add-on therapy, which has evidence for improving lung function (Evidence Level A). High-dose ICS-LABA is recommended for a trial period of 3-6 months only if good control is not achieved at medium-dose ICS-LABA with a third controller (LTRA or sustained-release theophylline).

At Step 5, treatment is phenotype-guided. The biologic options include:

• Omalizumab (anti-IgE): for allergic asthma with elevated IgE; subcutaneous injection every 2-4 weeks; dose based on serum IgE and body weight

• Mepolizumab (anti-IL-5): 100 mg SC every 4 weeks; for eosinophilic asthma ($\ge \backslash geq$ 300 cells/$\mu \backslash mu$L) in patients $\ge \backslash geq$ 12 years

• Benralizumab (anti-IL-5 receptor): 30 mg SC every 4 weeks for 3 doses, then every 8 weeks; for eosinophilic asthma $\ge \backslash geq$ 12 years

• Dupilumab (anti-IL-4R$\alpha \backslash alpha$): SC; for eosinophilic asthma $\ge \backslash geq$ 12 years

• Low-dose oral corticosteroid ($\le \backslash leq$ 7.5 mg/day prednisone equivalent): last resort due to osteoporosis risk; if used $\ge \backslash geq$ 3 months, start bone-protective counseling and therapy

Acute Exacerbation

The initial treatment triad is repeated inhaled SABA, early systemic corticosteroids, and supplemental oxygen. SABA is given as salbutamol 4-10 puffs via MDI with spacer every 20 minutes for the first hour. MDI with spacer provides equivalent bronchodilation to nebulizer for mild-moderate exacerbations (Evidence Level A) and is more cost-effective. However, severe acute exacerbations may require nebulization.

Oral corticosteroids (OCS) at a dose of 40-50 mg/day prednisone for 5-7 days should be started early. The guideline states OCS is indicated when the patient fails to respond to increased controller and reliever medications within 2-3 days, when PEF or $FE{V}_{1}FEV\_1$ drops rapidly to < 60% of predicted/personal best, or when there is a history of sudden severe exacerbations.

Ipratropium bromide is added to SABA for severe exacerbations or for patients who respond poorly to SABA alone. Meta-analysis shows the combination improves lung function and reduces hospitalization risk (Evidence Level B).

IV magnesium sulfate is considered for severe exacerbations not responding to initial therapy, particularly when $FE{V}_{1}FEV\_1$ or PEF remains < 50% predicted after the first hour.

Oxygen is titrated to a target $Sp{O}_{2}SpO\_2$ of 93-95% (94-98% in children). Saturations < 90% demand aggressive therapy.

ABG is not routine and is reserved for patients with PEF or $FE{V}_{1}FEV\_1$ < 50% predicted who do not respond to initial treatment.

Adrenaline (epinephrine) can be used for moderate-to-severe exacerbations when beta-2 agonists are unavailable or when the patient does not respond to SABA. However, it is not recommended for patients over 45 years old or with cardiovascular disease.

After exacerbation, patient discharge medications must include adequate reliever supply, OCS to complete the course, and for most patients, regular controller therapy. Follow-up evaluation should occur within 2-7 days. Controller therapy can generally be resumed at the pre-exacerbation level after 2-4 weeks, unless the exacerbation was preceded by chronically uncontrolled symptoms, in which case step-up is indicated.

05Differential Diagnosis & Distractors

06Traps & High-Yield Pearls

The single most commonly tested "gotcha" with adult asthma questions centers on misidentifying the treatment step or confusing severity with control. A vignette will describe a patient already on low-dose ICS-LABA who still has symptoms most days and wakes at night twice a week. The question asks for the "next best step." Many students incorrectly jump to adding biologics or oral corticosteroids (Step 5). The correct answer is almost always to step up one level (in this case, to medium-dose ICS-LABA and add tiotropium at Step 4) after first confirming proper inhaler technique and medication adherence. The Asma Dewasa PDPI 2021 repeatedly emphasizes that before any step-up, the clinician must verify five things: inhaler technique, medication adherence, allergen avoidance, management of comorbidities (rhinosinusitis, obesity, GERD, obstructive sleep apnea), and correct diagnosis.

The second major trap involves SABA monotherapy. A question may present a newly diagnosed asthma patient and offer "SABA as needed" as an answer choice. Per the Asma Dewasa PDPI 2021 (which adopts GINA 2020), SABA-only treatment is no longer recommended even at Step 1. The correct answer at Step 1 is low-dose ICS-formoterol as needed, or at minimum, low-dose ICS taken each time SABA is used. If you see "salbutamol inhaler as needed without any controller" as an answer choice, it is almost certainly the distractor.

Third, be alert for the silent chest trap. A vignette describes a patient with known asthma who presents in acute distress but the chest examination reveals absent breath sounds bilaterally. Students sometimes interpret this as "improving" or "no wheezing equals good." The opposite is true: a silent chest indicates such severe airway narrowing that insufficient air movement is occurring to generate wheezing. This is a life-threatening sign requiring ICU-level care, and the "next best step" is intubation preparation, not step-down of therapy.

Fourth, understand the concept of MART (Maintenance and Reliever Therapy): ICS-formoterol combination used as both daily controller AND as-needed reliever (with a cap of formoterol 72 mcg/day). This strategy is available only with budesonide-formoterol or beclomethasone-formoterol combinations. Vignettes testing this concept will present a patient using separate ICS and SABA inhalers who continues to have frequent exacerbations, and the correct management shift is consolidating to a single ICS-formoterol inhaler for both roles.

Finally, remember that the bronchial provocation test has high sensitivity but limited specificity. A negative methacholine challenge in a patient not on ICS effectively rules out asthma. A positive test, however, can also be seen in allergic rhinitis, COPD, and cystic fibrosis. The core competency being tested here is understanding negative predictive value versus positive predictive value when ordering confirmatory tests.