Evidence Level B
Randomized controlled trials (RCTs) of <200 participants, methodologically flawed RCTs of >200 participants, methodologically flawed systematic reviews (SRs) or good quality observational (cohort) studies.
Symptom severity: there is medium-quality evidence that use of short-acting beta agonists (SABA) 'as needed' is equally effective to regular use in reducing exacerbations and at improving daytime and night-time symptoms, and that regular-use of a SABA and 'as-needed' SABA are equally effective at improving lung function in people with chronic asthma.
More info from BMJ Clinical Evidence
