Impact of the global on patient perceivable change in an asthma specific QOL questionnaire.

One method of defining clinically meaningful changes in quality of life domain scores is 'anchoring', that is, relating changes in domain scores to more easily understood changes on a global question. Although this methodology has been used to assess changes in domain scores in clinical trials, the choice of global question has not undergone much scrutiny. This study examines the impact of two global questions on the definition of clinically meaningful changes in an asthma specific quality of life (ASQOL) questionnaire. We tracked 343 patients with mild to moderate asthma symptoms in a placebo controlled clinical trial. The patients responded to the ASQOL questionnaire, and answered two global questions; one assessing how well their asthma is controlled, and the other assessing the change in their asthma since the start of the study. Changes in each domain of the ASQOL questionnaire were related to each global question. Since each global question led to different definitions of what constituted meaningful change, we concluded that the wording of the global question can affect the definition of meaningful change in the ASQOL domain scores. Thus, when identifying meaningful changes, it is important to state the global question so that the context of the meaningful change is correctly understood.