Evidence Level C
Poor quality observational (cohort) studies or methodologically flawed randomized controlled trials (RCTs) of <200 participants.
Lung function: there is poor-quality evidence that adding theophylline to low-dose corticosteroids may be more effective than adding placebo at improving morning and evening peak expiratory flow rate (PEFR) in people with persistent asthma poorly controlled with inhaled corticosteroids. Adding theophylline is as effective as adding a long-acting beta2 agonist (LABA) to inhaled corticosteroids at improving FEV1 in people with poorly controlled moderate and persistent asthma.
More info from BMJ Clinical Evidence
