 - Patient has a diagnosis of asthma as defined by 1 an increase in FEV1 or PEF of 12 absolute value, 20 to 30 minutes after inhaled β-agonist administration, OR 2 a positive methacholine PC20 provocative concentration causing a 20 fall in FEV1 of 8 mgml or lower which was performed within the previous 12 months, OR 3 a fall in FEV1 of at least 15 after an exercise challenge which was performed within the previous 12 months. β-agonist reversibility and the methacholine and exercise challenge tests may be satisfied within the previous 12 months if there is adequate source documentation. 