 5. The patient has a positive reversibility test or history of such with or equal 15 improvement in FEV1 from 15 to 30 minutes after inhalation of at least 200 ug of salbutamol beta-2-adrenergic agonist administration or PEF variability of 20 as described in current BTSSIGN guidelines British Thoracic Society, Scottish Intercollegiate Guideline Network. British Guidelines on the Management of Asthma. Thorax 2003;58:1-94. 