VALIDATION OF AN ASTHMA QUALITY-OF-LIFE DIARY IN A CLINICAL-TRIAL

Background - Quality of life (QOL) is commonly measured in asthma clin ical trials by a questionnaire given before and after treatment. A str uctured asthma QOL daily diary provides more restricted information bu t on a daily basis. The validity and use of such a QOL diary was exami ned in a clinical trial in which two asthma treatments were compared. Methods - The effects of low dose inhaled steroid (400 mu g beclometha sone dipropionate, BDP) combined with the long acting beta(2) agonist salmeterol (100 mu g) (n = 220) was compared with high dose inhaled st eroid (1000 mu g BDP) (n = 206) in asthmatic outpatients in a double b lind, parallel group study. Outcome measures consisted of a combined d iary for peak expiratory flow (PEF) rate, symptoms, and problems, and an asthma-specific QOL questionnaire, the Living with Asthma Questionn aire. Results - The QOL diary correlated with the QOL questionnaire fo r both cross sectional and longitudinal assessments. Cross sectional c orrelations with PEF were higher for the QOL questionnaire than the QO L diary, but longitudinal correlations with PEF were higher for the di ary than the questionnaire. Treatment with low dose steroid/salmeterol compared with high dose steroid produced better lung function, better QOL as measured by diary, and reduced night time wakenings, but treat ment differences were not obtained with the QOL questionnaire nor for daytime symptoms. Diary assessed QOL was a better predictor of low PEF than diary assessed symptoms. Compliance with diary completion was go od but there were floor or ceiling effects in the QOL diary records of about 25% of patients. Conclusions - Structured QOL diaries are valid instruments that appear to be more responsive to longitudinal change in clinical trials than a QOL questionnaire, but QOL questionnaires pr ovide a more sensitive cross sectional measure of disease severity. Fl oor and ceiling effects are found in some patients' QOL diaries which limit their usefulness. QOL diary problem events occur during the trou ghs of a peak flow graph, while symptoms are more widely distributed w ith respect to peak flow.