Bronchial asthma can be diagnosed by-a) Wheezeb) Dyspneac) Normal FEV1d) Coughe) Reversible obstruction

**Core Concept**
Bronchial asthma is a chronic inflammatory disease of the airways characterized by episodic airflow limitation, which is reversible either spontaneously or with treatment. This condition is associated with airway hyperresponsiveness, inflammation, and remodeling.

**Why the Correct Answer is Right**
The correct answer is **(e) Reversible obstruction**. In bronchial asthma, airflow limitation is reversible, which is a key diagnostic criterion. This reversibility can be demonstrated by a significant improvement in FEV1 (forced expiratory volume in one second) after administration of a bronchodilator or corticosteroid. The underlying mechanism involves the relaxation of airway smooth muscle, reduction of airway inflammation, and normalization of airway function.

**Why Each Wrong Option is Incorrect**
* **Option A:** Wheeze is a common symptom of bronchial asthma, but it is not a diagnostic criterion. Wheezing can also occur in other conditions, such as chronic obstructive pulmonary disease (COPD) or heart failure.
* **Option B:** Dyspnea (shortness of breath) is a symptom of bronchial asthma, but it is not a specific diagnostic criterion. Dyspnea can occur in many conditions, including respiratory and cardiac diseases.
* **Option C:** Normal FEV1 is not a diagnostic criterion for bronchial asthma. In fact, patients with asthma often have reduced FEV1 during exacerbations, which improves with treatment.
* **Option D:** Cough is a common symptom of bronchial asthma, but it is not a diagnostic criterion. Cough can occur in many conditions, including respiratory and cardiac diseases.

**Clinical Pearl / High-Yield Fact**
A key clinical pearl is that bronchial asthma is often characterized by a triad of symptoms: wheezing, cough, and shortness of breath. However, the diagnosis of asthma requires demonstration of reversible airflow limitation, which can be assessed using spirometry or other diagnostic tests.

**Correct Answer:** E. Reversible obstruction