The relationship between health-related quality of life, lung function and daily symptoms in patients with persistent asthma.

It is generally believed that there is a direct correlation between asthma control and a patient's health-related quality of life (HRQL). Objective and subjective measures of asthma control are used interchangeably. A retrospective analysis from 8994 patients from 27 randomized, controlled clinical trials with persistent asthma was conducted to determine the degree of association which exists between objective (lung function) and subjective (symptoms, quality of life) measures. Assessments were made via forced expiratory volume in 1-second (FEV1), self-reported symptoms and the Asthma Quality of Life Questionnaire (AQLQ) overall scores. Baseline percent predicted FEV1 was weakly correlated with baseline symptom-free days (SFD) and baseline overall AQLQ scores (r=0.11 and 0.09, respectively; P <0.001). Changes in percent predicted FEV1 correlated weakly with changes in SFD but was more strongly correlated with changes in overall AQLQ scores (r= 0.26 and 0.38, respectively; P <0.001). Additionally, SFD at both baseline and endpoint were moderately correlated with overall AQLQ scores at baseline and endpoint (r=0.36 and 0.44; P <0.001). This study suggests that the impact of asthma on a patients' HRQL is not fully accounted for by objective measures such as lung function. Thus, HRQL data complements rather than duplicates results from traditional, objective assessments of asthma control.