Dimensions and attributes used in QALY instruments: a systematic review

Economic assessment is highly important in healthcare decision-making process. The quality-adjusted life-year (QALY) concept provides a rare opportunity to combine two crucial aspects of health, i.e., mortality and morbidity, into a single index, in order to perform cost-utility comparison. Today, many tools are available to measure morbidity in terms of health-related quality of life (HRQoL) and a large literature describes how to use them. Recently, the Coronavirus disease 2019 (Covid-19) pandemic challenged all healthcare systems and recommended measures (e.g., confinement, social distancing) that produced negative effects on population’s health as regards to HRQoL. To correctly assess this impact of the virus, it is important to use the most relevant QALY instruments. Hence, understanding their characteristics and development process is a key point. In this aim, we conducted a systematic review and 40 studies were selected after searches done in four databases: Medline EBSCO, Scopus, ScienceDirect and PubMed. The search procedure ended on June 18, 2020. We mainly focused on the type of instrument developed, the number and the nature of dimensions and levels retained, the elicitation method and the model used to determine utility scores, and the instrument and algorithm validation methods. Results show that studies which treated the development of specific instruments were motivated by inappropriateness of generic instruments in those fields. For the dimensions’ and levels’ selection, the item response theory, the Rasch analysis and literature review were mostly used. Dimensions and levels were validated by methods like the Loevinger H, the standardised response mean or discussions with fields’ experts. The time trade-off method was the most widely used elicitation method followed by the visual analogue scale and random effects regression models served a lot in determining utility scores.