There is no single precise test to diagnose asthma,hence has to be based on patterns of symptoms and response to therapy over the time.However Spirometry test aids in asthma diagnosis and its management .In this test Forced Expiration Volume in 1 second [FEV1] is measured followed by administration of bronchodilator like salbutamol . If the improvement in FEV1 is greater than 12% it is supportive of diagnosis