BACKGROUND: The Asthma Quality of Life Questionnaire (AQLQ) and the Asthma Control Questionnaire (ACQ) are widely used in asthma research; however, in studies of newer asthma treatments, mean improvements in these measures compared with placebo arms do not exceed the minimal important difference (MID), particularly when a new treatment is added to current treatment.
OBJECTIVE: We performed a systematic review and network meta-analysis to examine the magnitude of AQLQ and ACQ responses achieved with commonly used asthma drugs and factors influencing these end points in clinical trials.
METHODS: A systematic literature search was conducted to identify blinded randomized controlled trials reporting AQLQ or ACQ results. Mixed treatment comparisons, combined with meta-regression, were then performed.
RESULTS: Of the 64 randomized controlled trials (42,527 patients) identified, 54 included the AQLQ and 11 included the ACQ as end points. The presence of a run-in period, the nature of treatment during the run-in period, concurrent treatment during the treatment period, and instrument version significantly influenced the change in AQLQ score from baseline and whether it exceeded the MID. When compared with placebo, only inhaled corticosteroids (ICSs), with or without a long-acting β-agonist, achieved the MID. The ACQ results were comparable with those of the AQLQ: no differences from placebo exceeded the MID, and ICS-based treatments provided the greatest improvements.
CONCLUSION: The established within-patient MID for the ACQ and AQLQ is not achievable as a group-wise efficacy threshold between treatment arms in clinical studies in which controllers are added to ICS treatment. Thus in addition to reporting mean changes of the instruments, other measurement criteria should be considered, including responder analyses.
