In Asthma patient positive bronchodilator reversibility test is indicated by
**Core Concept**
The bronchodilator reversibility test is a diagnostic tool used to assess the reversibility of airflow limitation in patients with asthma. It measures the change in forced expiratory volume in one second (FEV1) after administration of a bronchodilator.
**Why the Correct Answer is Right**
The test is considered positive if there is a significant increase in FEV1 of at least 12% and 200 mL after inhalation of a bronchodilator. This indicates that the airway obstruction is reversible, which is a hallmark of asthma. The increase in FEV1 is due to the relaxation of bronchial smooth muscle and opening of airways, allowing for easier airflow.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a positive bronchodilator reversibility test is not indicated by a decrease in FEV1, which would suggest a non-reversible airway obstruction.
**Option B:** This option is incorrect because a bronchodilator reversibility test is not typically used to diagnose chronic obstructive pulmonary disease (COPD), which is a different respiratory condition.
**Option C:** This option is incorrect because a bronchodilator reversibility test is not indicated by a normal FEV1, which would suggest that the patient does not have asthma.
**Clinical Pearl / High-Yield Fact**
A positive bronchodilator reversibility test is a crucial diagnostic criterion for asthma, and it helps differentiate asthma from other respiratory conditions.
**Correct Answer:** C.