[New clinical indicators. Health-related quality of life]

In the last decades the need of better measurements of health outcomes has increased the interest for new clinical indicators. Health-related quality of life (HRQoL) has emerged in this context as a multidimensional model approach where the patient is the exclusive source of information. The main objective of HRQoL measurement is to provide a global evaluation of the impact of diseases and the consequences of treatments over the daily life of the patients. The instruments developed for that purpose are questionnaires; either generic--for the comparison between different diseases-, or specific--aimed to evaluate particular conditions. These questionnaires must demonstrate several psychometric properties, such as reliability, validity, responsiveness, and for some authors also feasibility. In many areas, HRQoL studies have demonstrated to increase the knowledge of the natural history of diseases and its global consequences, beyond the classic health outcomes information based on morbidity and mortality rates. This knowledge may assist in the design of epidemiological studies and improve the comparison of strategies in therapeutic interventions. Nevertheless, some controversial issues remain such as the clinical implications of absolute scores obtained, and the need for updating the content of the instruments in accordance with the changes in natural history of diseases under evaluation.