<prompt> In a Patient with clinical signs of Asthma which of the following tests will confirm the diagnosisIncrease in FEVUFVC200 ml increase in FEV I after MethacholineDiurnal variation in PEF 20 PercentReduction of FEV 1 20 after bronchodilatces  <response>: Ans. is c i.e., Diurnal variation in PEF 20 Percent Diagnosis of Asthma require Demonstration of Airways obstruction Decrease in the ratio of FEVIFVc Demonstration of acute reversibility of airflow Administer 2-4 puffs of quick acting bronchodilator e.g., albuterol and repreat spirometry 10-15 min An increase in FEV , of 12 or more accompanied by an absolute increase in FEV,of at least 20 ml Demonstration of Airway hyperresponsiveness in response to methacholine challenge test A bronchoprovocator Methacholine is administered hyperresponsiveness of the airway is demonstrated by reduction of FEV1 to 20 Increased Peak expiratory flow rate variabilities Demonstration of diurnal variation in PEF of more than 20 strongly suggests diagnosis of Asthma 