[Quality of life and its measurement]

At present quality of life has a significant place within health care and scientific research work. This interest is stimulated by the fact that people want to live, not just to survive. The problem of quality of life in persons whose lives could not be preserved, opens discussions concerning artificial subsistence of life, euthanasia etc. This is not a new topic. What is new is development of official ways to measure quality of life and their routine application.

In general, quality of life can be defined as the level of well-being. It cannot be identified with health, but probably primarily with ability to conduct an economically and socially productive life. Quality of life refers to physical, psychological and social domains of health, being influenced by one's experience, beliefs, expectations and perceptions. There is no consensus concerning the concept of quality of life and according to the same authors it includes functional ability, level and quality of social interactions, physical welfare, somatic sensations and life satisfaction. Generally speaking concepts include numerous dimensions and possibilities occurring during life, to death itself (Table 1). Although objective dimension of health is important in assessment of patient's health, subjective estimation and expectations make, what is found to be an objective situation, experienced quality of life (Graph. 1).

The most difficult task is to present various segments of health into quantitative values. All data can be measured at nominal, ordinal, interval or ratio scales. The nominal scale uses numbers and other symbols in classification of characteristics. Categories cannot be classified according to volume and are mutually exclusive. Ordinal scales are used when measuring a limited number of categories classified according to quality. Interval scales measure an unlimited number of categories with equal intervals and they are without a real zero point. Ratio scales have all the characteristics of interval scales, but they have real zero points.

There are different instruments to assess quality of life such as generic instruments, battery scales and modular instruments index methods and instruments. The measuring instruments should be reliable, valid, responsive and sensitive.

Three design studies are most frequently used: cross-sectional or nonrandomized longitudinal studies, randomized studies of clinical interventions and cost-effective and cost benefit analyses.