Validity of two common asthma-specific quality of life questionnaires: Juniper mini asthma quality of life questionnaire and Sydney asthma quality of life questionnaire

BACKGROUND This study explored the psychometric properties (internal consistency, construct validity, discriminative ability) of the Juniper Mini Asthma Quality of Life Questionnaire (Mini AQLQ-J) and the Sydney Asthma Quality of Life Questionnaire (AQLQ-S). METHODS One hundred fourty-six adults (18-45 years) with asthma requiring regular inhaled corticosteroids were recruited to a trial of written emotional disclosure. Correlational analyses were performed to understand the relationship of the two measures with each other, with symptoms, lung function, asthma control, asthma bother and generic quality of life. Median quality of life scores were compared according to gender, health care usage and levels of asthma severity. RESULTS AQLQ-J and AQLQ-S total scores correlated strongly with each other (rho = -0.80) and moderately with the EuroQol Current Health Status Scale (AQLQ-J: rho = 0.35; AQLQ-S: rho = -0.40). Domain score correlations between AQLQ-J and AQLQ-S were mostly moderate (0.50 < rho < 0.80).Both QoL measures were significantly correlated with symptom score. Correlations with the symptom score asthma module (AQLQ-J: rho = -0.69; AQLQ-S: rho = 0.50) were stronger compared with the total symptom score and the symptom score rhinitis module (AQLQ-J: rho = -0.41; AQLQ-S: rho =0.31).Neither QoL measure was significantly correlated with FEV1, % predicted at the total or the domain level.Total scores of both measures were significantly correlated with subjective asthma control (AQLQ-J: rho = 0.68; AQLQ-S: rho = -0.61) and asthma bother (AQLQ-J: rho = -0.73; AQLQ-M: rho = 0.73).Total AQLQ-J score and total AQLQ-S score were significantly associated with perceived asthma severity (AQLQ-J: p=0.004, AQLQ-S: p=0.002) and having visited a GP in the past four months (AQLQ-J: p=0.003, AQLQ-S: p=0.002). CONCLUSIONS This study provides further evidence for the validity of the AQLQ-J and the AQLQ-S in a British population of adult patients with asthma managed in primary care. Correlations with lung function parameters were weak or absent. Correlations with generic quality of life were moderate, those with asthma symptoms, asthma control and asthma bother were strong. Both measures are able to discriminate between levels of asthma severity and health care usage.