CONSTRUCTING HEALTH STATE PREFERENCE VALUES FROM DESCRIPTIVE QUALITY-OF-LIFE OUTCOMES - MISSION IMPOSSIBLE

Descriptive quality of life questionnaires are commonly administered i n clinical trials, to evaluate outcomes from the patient's perspective alongside conventional clinical measures. When expressed in single in dex form as health state preference values (HSPVs), quality of life in formation is also relevant to economic evaluations. By combining HSPVs with survival information, quality adjusted life years (QALYs) may be derived for cost-utility analysis, Although HSPVs are rarely measured prospectively in cancer clinical trials, the UK Medical Research Coun cil Cancer Therapy Committee recommends the routine administration of two specific quality of life questionnaires: the Rotterdam Symptom Che ck-list and the Hospital Anxiety Depression Scale. This study explores two potential methods for secondary derivation of HSPVs from these in struments, using data gathered in a clinical trial of two forms of rad iotherapy for non-small cell cancer of the bronchus. The first method, secondary mapping to existing utility scales, was found to be infeasi ble from the above questionnaires. The second method used factor analy sis to summarize the descriptive quality of life data collected throug h the questionnaires. This revealed five distinct factors prevalent in the trial population. Using these factors, simplified health state sc enarios were developed from which direct measurement of HSPVs was feas ible. As the resulting HSPVs and any QALYs that may be derived from th em are cancer specific, their potential value in informing resource al location would be limited to decisions within oncology services.